sit up

Từ điển Oxford Advanced Learner 8th

▪ I. ˌsit ˈup derived
1. to be or move yourself into a sitting position, rather than lying down or leaning back
•Do you feel well enough to sit up yet?
•Sit up straight— don't slouch.
2. to not go to bed until later than usual
•We sat up half the night, talking.
Main entry: ↑sit_derived
 
▪ II. ˌsit ˈup (and do sth) derived
(informal)to start to pay careful attention to what is happening, being said, etc
•The proposal had made his clients sit up and take notice.
Main entry: ↑sit_derived