stay up

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stay up (third-person singular simple present stays up, present participle staying up, simple past and past participle stayed up)

1. Used other than figuratively or idiomatically: see stay,‎ up.

   These trousers are too big around the waist. They won't stay up.

2. (intransitive) To remain awake, to not go to bed.

   My plane leaves at 6:00 in the morning, so I plan to stay up until then and sleep on the plane.

   She stayed up past her bedtime.

3. (intransitive, euphemistic) To maintain an erection.

   He told his lover he has a problem staying up.

• stay up late

• upstay