Idioms Beginning With 'O'

Object lesson
An object lesson serves as a warning to others. (In some varieties of English 'abject lesson' is used.)
Odds and ends
Odds and ends are small, remnant articles and things- the same as 'bits and bobs'.
Off colour
If someone looks off colour/color, they look ill.
Off the beaten track
Somewhere that's off the beaten track is in a remote location.
Off the chart
If something goes off the chart, it far exceeds the normal standards, good or bad, for something.
Off the cuff
If you do something off the cuff, you do it without any preparation.
Off the grid
Someone who is off the grid lives outside society and chooses not to follow its rules and conventions.
Off the hook
If someone is off the hook, they have avoided punishment or criticism for something they have done.
Off the mark
If something is off the mark, it is inaccurate or incorrect.
Off the rails
If someone has gone off the rails, they have lost track of reality.
Off the record
Something off the record is said in confidence because the speaker doesn't want it attributed to them, especially when talking to the media.
Off the scale
If something goes off the scale, it far exceeds the normal standards, good or bad, for something.
Off the shelf
If a product is off the shelf, it can be used straightaway without any setting-up.
Off the top of your head
If you say something off the top of your head, you don't think about it beforehand.
Off the track
If something puts or throws you off your track, it distracts you or keeps you from achieving what you want.
Off the wall
Something that is off the wall is unconventional.
Off your chump
(UK) If someone is off their chump, they are crazy or irrational.
Off your rocker
(UK) Someone who is off their rocker is crazy.
Off-hand
Off-hand means without preparation. People say that they don't know the answer off-hand, meaning that they don't know it at that time.
Oh, my goodness!
An expression of surprise.
Old chestnut
An old chestnut is something that has been repeated so many times that it has lost its impact.
Old flames die hard
It's very difficult to forget old things, especially the first love.
Old friends and old wine are best
This idiom means that the things and people that we know well are better than the unfamiliar.
Old hat
If something's old hat, it seems rather old fashioned and dated.
Old wive's tale
A proverb or piece of advice that is commonly accepted as truth and is handed down the generations, but is normally false.
Oldest trick in the book
The oldest trick in the book is a well-known way of deceiving someone, though still effective.
Olive branch
If you hold out or offer an olive branch, you make a gesture to indicate that you want peace.
On a fishing expedition
If someone is on a fishing expedition, they are trying to get information, often using incorrect or improper ways to find things out.
On a roll
If you're on a roll, you're moving from success to success.
On a silver platter
If you hand or give something on a silver platter to someone, you let them have it too easily.
On all fours
If someone is on all fours, they crawl.
On Carey Street
(UK) If someone is on Carey Street, they are heavily in debt or have gone bankrupt.
On good terms
If people are on good terms, they have a good relationship.
On hold
If something is on hold, no action is being taken.
On ice
If plans are put on ice, they are delayed and no action will be taken for the foreseeable future.
On pins and needles
If you are on pins and needles, you are very worried about something.
On tenterhooks
This means that she is waiting impatiently and excitedly for something.
On the ball
If someone's on the ball, they are well-informed and know what's going on in their area of responsibility or interest.
On the blink
(UK) Is a machine is on the blink, it isn't working properly or is out of order.
On the blower
(UK) If someone is on the blower, they are on the phone.
On the cards
(UK) If something is in the cards, it is almost certain to happen.
On the carpet
When you are called to the bosses office (since supposedly, they are the only ones who have carpet) and its definitely not for a good reason, i.e., you are in trouble, something has not gone according to plan and either maybe you are responsible and/or have some explaining to do.
On the case
If someone is on the case, they are dealing with a problem.
On the cheap
If you do something on the cheap, you spend as little as possible to do it.
On the dole
(UK) Someone receiving financial assistance when unemployed is on the dole.
On the dot
If someone says that they're leaving at seven on the dot, don't be late; they mean at exactly seven o'clock.
On the factory floor
On the factory floor means the place where things are actually produced.
On the fiddle
(UK) Someone who is stealing money from work is on the fiddle, especially if they are doing it by fraud.
On the flip side
On the reverse or the other side
On the fly
If you do things on the fly, you do things without preparation, responding to events as they happen.
On the game
(UK) A person who is on the game works as a prostitute.
On the ground
Events on the ground are where things are actually happening, not at a distance.
On the hoof
If you decide something on the hoof, you do it without planning, responding to events as they happen.
On the house
If you get something for free that would normally have to be bought, especially in a bar or restaurant, it is on the house.
On the lam
If someone is on the lam, they are hiding from the police or authorities, especially to avoid arrest or prison.
On the level
If someone is honest and trustworthy, they are on the level.
On the line
If somebody's job is on the line, they stand a very good chance of losing it.
On the make
If someone is on the make, they are trying to make a lot of money, usually illegally.
On the map
If a place becomes widely known, it is put on the map. A place that remains unknown is off the map.
On the money
If you are on the money, you are right about something.
On the never-never
(UK) If you buy something on the never-never, you buy it on long-term credit.
On the nod
(UK) If something is accepted by parliament or a committee majority, it is on the nod.
On the nod
(UK) Someone who's on the nod is either asleep or falling asleep, especially when the shouldn't or are are in a position unusual for sleep, like sitting or standing.
On the nod
(UK) When a horse runs, its head moves backwards and forwards alternately - in horse racing, if 2 horses cross the line together the one whose head happens to be going forward often wins and is said to win 'on the nod'.
On the nose
This means right on time.
On the rebound
If someone is on the rebound, their relationship has recently ended and they are emotionally unstable.
On the right foot
If you start something or set off on the right foot, you get off to a good start.
On the ropes
When something or someone is on the ropes, it or they are doing badly and likely to fail.
On the run
If someone is on the run, they are avoiding arrest and hiding from the police.
On the same page
If people are on the same page, they have the same information and are thinking the same way.
On the same wavelength
If people are on the same wavelength, they have the same ideas and opinions about something.
On the shelf
If something like a project is on the shelf, nothing is being done about it at the moment.
On the skids
When things or people are on the skids, they are in serious decline and trouble.
On the sly
If someone does something on the sly, they do it furtively or secretly.
On the stump
When politicians are campaigning for support and votes, they are on the stump.
On the take
(UK) Someone who is stealing from work is on the take.
On the tip of your tongue
If a word is on the tip of your tongue, you know you know the word, but you just can't quite remember it at the moment.
On the trot
(UK) This idiom means 'consecutively'; I'd saw them three days on the trot, which means that I saw them on three consecutive days.
On the up and up
If you are on the up and up, you are making very good progress in life and doing well.
On the wagon
If someone is on the wagon, they have stopped drinking alcohol.
On the wallaby track
(AU) In Australian English, if you're on the wallaby track, you are unemployed.
On top of the world
If you are on top of the world, everything is going well for you.
On your high horse
When someone is on their high horse, they are being inflexible, arrogant and will not make any compromises.
On your last legs
If someone's on their last legs, they're close to dying.
On your soapbox
If someone is up on their soapbox about something, they are very overtly and verbally passionate about the topic.
On your tod
If you are on your tod, you are alone.
On your toes
Someone on his or her toes is alert and ready to go.
Once bitten, twice shy
If somebody is said to be once bitten twice shy, it means that someone who has been hurt or who has had something go wrong will be far more careful the next time.
Once in a blue moon
If something happens once in a blue moon, it happens very rarely indeed.
One bad apple
The full form of this proverb is 'one bad apple spoils the barrel', meaning that a bad person, policy, etc, can ruin everything around it.
One fell swoop
If something is done at one fell swoop, it is done in a single period of activity, usually swiftly and ruthlessly.
One for the road
A last drink before leaving a pub or bar is one for the road.
One good turn deserves another
This means that when people do something good, something good will happen to them.
One hand washes the other
This idiom means that we need other people to get on as cooperation benefits us all.
One man's loss is another man's gain
This means thato ne person's setback benefits someone else.
One man's meat is another man's poison
This idiom means that one person can like something very much, but another can hate it.
One man's trash is another man's treasure
What is useless to one person might be valuable to another.
One over the eight
(UK) Someone who is one over the eight is drunk.
One swallow does not make a summer
This means that one good or positive event does not mean that everything is all right.
One-man band
If one person does all the work or has all the responsibility somewhere, then they are a one-man band.
One-off
A one-off event only happens once and will not be repeated.
One-trick pony
A one-trick pony is someone who does one thing well, but has limited skills in other areas.
Oops a daisy
An expression used to indicate surprise.
Open all hours
If a shop or suchlike is open all hours, it only closes, if at all, terribly late.
Open book
If a person is an open book, it is easy to know what they think or how they feel about things.
Open old sores
When a sore is almost healed, and if a person rips or tears it open, it is way of preventing the healing process and further aggravating the pain. This phrase, metaphorically suggests, to revive or reopen a quarrel or enmity which was almost forgotten.
Open old wounds
If you open old wounds, you revive a quarrel or problem that caused a lot of trouble in the past.
Opening a can of worms
If you open a can of worms, you do something that will cause a lot of problems and is, on balance, probably going to cause more trouble than it's worth.
Opportunity knocks but once
This idiom means that you only get one chance to achieve what you really want to do.
Other fish to fry
If you have other fish to fry, it doesn't matter if one opportunity fails to materialise as you have plenty of others.
Other side of the coin
The other side of the coin is a different, usually opposing, view of a situation. ('Flip side of the coin' is an alternative.)
Out and about
If someone is out and about, they have left their home and are getting things done that they need to do.
Out in the sticks
(UK) If someone lives out in the sticks, they live out in the country, a long way from any metropolitan area.
Out like a light
If you are out like a light, you fall fast asleep.
Out of hand
If something gets out of hand, it gets out of control.
Out of my league
If someone or something is out of your league, you aren't good enough or rich enough, etc, for it or them.
Out of pocket
If you are out of pocket on a deal, you have lost money.
Out of sight, out of mind
Out of sight, out of mind is used to suggest that someone will not think or worry about something if it isn't directly visible or available to them.
Out of sorts
If you are feeling a bit upset and depressed, you are out of sorts.
Out of the blue
If something happens out of the blue, it happens suddenly and unexpectedly.
Out of the box
Thinking out of the box is thinking in a creative way. However, it can also be used for a ready-made product that requires no specialist knowledge to set it up.
Out of the frying pan, into the fire
If you get out of one problem, but find yourself in a worse situation, you are out of the frying pan, into the fire.
Out of the gate running
If someone comes out of the gate running, they start something at a fast pace, without any build-up.
Out of the left field
(USA) If something comes out of the left field, it is beside the point and has nothing to do with the matter being discussed.
Out of the mouths of babes
People say this when children unexpectedly say something very intelligent or wise.
Out of the woods
If you are out of the woods, you have emerged safely from a dangerous situation, though the idiom is often used in the negative.
Out of this world
If something is out of this world, it is fantastic.
Out of Whack
If something is out of whack, it is not working correctly or not in the correct order.
Out of your hair
If you get someone out of your hair, you get them to stop bothering or annoying you. ('Stay/keep/get out of my hair!' can be used as imperatives)
Out of your mind
If someone is out of the mind, they are so emotional about something that they are no longer rational.
Out of your own pocket
If someone does something out of their own pocket, they pay all the expenses involved.
Out on a limb
If somebody's out on a limb, they are in a very exposed position and could get into difficulties.
Out to lunch
If someone's out to lunch, they are crazy or out of touch.
Out-and-out
This means complete or total; an out-and-out lie is completey false.
Over a barrel
If someone has you over a barrel, they have you in a position where you have no choice but to accept what they want.
Over and over
If something happens over and over, it happens repeatedly.
Over my dead body
If you say that something will happen over your dead body, you will not let it happen.
Over the counter
Medicines and drugs that can be sold without a doctor's prescription are sold over the counter.
Over the hill
If someone is over the hill they have reached an age at which they can longer perform as well as they used to.
Over the moon
If you are over the moon about something, you are overjoyed.
Over the top
If something is over the top, it is excessive or unnecessary. It refers to the moment a soldier leaves the trenches.
Over your head
If something is over your head, or goes over your head, it is too complex or difficult for you to understand.
Over-egg the pudding
(UK) If you over-egg the pudding, you spoil something by trying to improve it excessively. It is also used nowadays with the meaning of making something look bigger or more important than it really is. ('Over-egg' alone is often used in this sense.)