wait up phrasal verb (
see also wait)
1. to wait for someone to return before you go to bed
wait up for
Don’t wait up for me; I may be late.2. Wait up! American English used to tell someone to stop, so that you can talk to them or go with them:
‘Wait up!’ he called. [TahlilGaran] Dictionary of Contemporary English ▲
wait up v. phr. To not go to bed until a person one is worried about comes home (said by parents and marriage partners).
My mother always waited up for me when I went out as a young student. She always waits up for her husband when he's out late. [TahlilGaran] English Idioms Dictionary ▲