wait up

Từ điển Oxford Advanced Learner 8th

▪ I. ˌwait ˈup derived
(NAmE)used to ask sb to stop or go more slowly so that you can join them
•Wait up— you're walking too fast for me.
Main entry: ↑wait_derived
 
▪ II. ˌwait ˈup (for sb) derived
to wait for sb to come home at night before you go to bed
•I'll be back very late so don't wait up for me.
Main entry: ↑wait_derived