go to bed, turn in, bed, crawl in, kip down, hit the hay, hit the sack, sack out, go to sleep, retire(verb)

prepare for sleep

"I usually turn in at midnight"; "He goes to bed at the crack of dawn"

go to sleep(Verb)

To fall asleep

go to sleep(Interjection)

An expression used to dismiss an extremely foolish statement, or to dismiss somebody that one does not feel like talking to.