Idioms beginning with U. Select an idiom for more details.

an unknown quantity

If a thing or a person is an unknown quantity, not much is known about them.

an uphill battle | struggle | task

If doing something is an uphill battle, an uphill struggle or an uphill task, it is difficult to do because of obstacles such as opposition from other people.

the upper crust

If you are one of the upper crust, you are a member of society's highest class.

the upper hand

If you have the upper hand, you have the advantage or you're in the stronger position in a contest or a conflict.

the ups and downs

If you talk about "the ups and downs" in someone's life, or during a period of time, you talk about both the good times and the bad times.

um and ah British English

If you "um and ah" you're having trouble deciding what to say, or you're having trouble telling somebody something.

under a cloud

If someone is under a cloud, they are suspected of having done something wrong.

under fire

You're under fire if you're being attacked by the media or cricitised by many people.

under lock and key

If something is under lock and key, it is kept in a very secure place.

under no circumstances

If you are told that under no circumstances should you do something, you must never do it, no matter what happens.

under the table American English

If something is done under the table, it's done secretly, usually because it's illegal or unethical.

under the weather

If you are under the weather, you're not feeling well.

under wraps

If something is under wraps, it's being kept secret.

under your own steam

If you do something under your own steam, you do it without anybody's help.

up a gum tree Australian English

If you're up a gum tree, you're in trouble or have a serious problem.

up and running

You can say something like a system or an organisation is up and running if it has started to operate.

up for grabs INFORMAL

If something is up for grabs, it's available for anyone who wants to try to get it.

up in arms

If you are up in arms, you are angry about something that you think is unfair or wrong.

up in the air

If something such as a plan to do something, or details of an agreement, are up in the air, they still haven't been decided or settled yet.

up to no good INFORMAL

If someone is up to no good, they are doing something bad, or something wrong.

up to scratch | up to snuff INFORMAL

You can say something is up to scratch, or up to snuff, if it's as good as it should be, or as good as it needs to be.

up to your neck | up to your eyeballs

If you're up to your neck in something, or up to your eyeballs in something, you've got too much of it and it's become a problem.


If someone's up-and-coming, they show signs of being successful in their profession.

upset the applecart

If you upset the applecart, you do something that causes trouble or upsets someone's plans.


When we say something is user-friendly, we mean it is easy to use.

Contributor: Matt Errey