Meaning of “lie in” - Learner’s Dictionary

lie in

UK phrasal verb with lie uk us /laɪ/ verb [ I ] (present participle lying, past tense lay, past participle lain)

to stay in bed in the morning later than usual:

I lay in till eleven o'clock this morning.

(Definition of “lie in phrasal verb, verb” from the Cambridge Learner’s Dictionary © Cambridge University Press)