check in verb 9/ˈt͡ʃɛkˌɪn/ noun 3forms 4 verb9 •To announce or record one's own arrival at a hotel, airport etc.We got to the hotel last night and checked in at the front desk. •To verify a person's information and record their arrival, such as at a hotel, airport, etc.The clerk checked us in at the front desk. •To contact another person in order to keep the other person informed of one's situation.Kelly has to check in with her parole officer today. •To visit in order to see how someone is doing.I just wanted to check in after your accident. How are you recovering? •To return (a book to a library, source code to a repository, etc.). •To integrate new revisions into the public or master version of a file in a version control system. •to tap on, to touch in, to tap in (to use a smartcard to start a public transport journey)You can check in and check out with a contactless debit card or credit card. Registering in advance is not necessary. — 2025 •(slang) To enter solitary confinement at one's own request for protection from other prisoners.If an authority exists other than that of the pigs, gay victims of homophobia will not have to check in (into protective custody). — 1980 •(slang) To send somebody to solitary confinement; to make somebody be admitted to solitary confinement. check-in /ˈt͡ʃɛkˌɪn/ noun3 •The act of checking in at a hotel, airport, etc.The hotel never charges for a late check-out or for an early check-in . . . — 2004 •The act of contacting another person in order to keep them informed of one's situation. •The submission of source code or other material to a source control repository. formschecked in · checking in · checks in · check-ins