check sth in
phr. v..phr. v.. To register your arrival at a hotel or airport. You also use this phrase when you give your luggage to an airline before a flight.
phr. v.. To register one's arrival at a hotel or airport (intransitive), or to entrust one's luggage to an airline for transport (transitive and separable).
We need to check in our bags.
Please have your passport ready when you check in your luggage at the counter.
The airline's policy requires passengers to check in any bag weighing over 10 kilograms, which can be done online or at the airport.
Often used intransitively for people ('we checked in') and transitively for luggage ('check in your bags').
Contrast with 'check out' (to leave a hotel) and 'check on' (to see if someone is okay); the opposite action for luggage is 'claim' or 'collect'.
I checked in it at the desk.I checked it in at the desk.When the object of a separable phrasal verb is a pronoun (like 'it'), it must go between the verb and the particle.