D defs.my
Entry 1 sense Webster, 1913

check in

/(chĕk`ĭn")/ · check· in · IPA
01 v. i. To register as a guest at a hotel, inn, motel. etc. Converse of check out.
  1. 1.
    To register as a guest at a hotel, inn, motel. etc. Converse of check out.