From WordNet (r) 2.0 (August 2003) [wn]:
check-in
n : the act of reporting your presence (as at an airport or a
hotel)
From The Collaborative International Dictionary of English v.0.48 [gcide]:
check-in \check"-in\ (ch[e^]k"[i^]n), n.
The act of registering as a guest at a hotel, inn, motel.
etc; the act of checking in. Used also attributively, as the
check-in counter at a hotel.
[PJC]