- (literally) To remain in a raised or upright position.
- These trousers are too big around the waist. They won't stay up.
- 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.
- (euphemistic) To maintain an erection.
- He told his lover he has a problem staying up.