happening during, as a result of or according to a particular situation, event, rule, etcThe work was completed under very difficult conditions.
Now that the deadline is approaching we all feel under pressure.
The chair broke under his weight (= because he was too heavy for it).
Under the present rules, you can buy ten litres of wine.
under attack/consideration/discussion, etc. in the process of being attacked, considered, discussed, etcThe town is under fire (= is being attacked) from the air.
The proposals are now under consideration by the Board of Governors.
The situation is still not under control.
under sedation/the doctor, etc. UK treated in the way mentioned or by the medical person mentionedThe patient is being kept under heavy sedation.
She'll have to go under anaesthetic for the operation.
old-fashioned She's been under the doctor for a viral infection.
be under an impression/belief to believe something, often wronglyHe was under the mistaken belief that I was in charge.