look up anything, like your first name:
1. Check in
Determining if someone is all right or on task.

Asking everyone in a meeting to tell one by one how they are doing.
I'll check in with you after work.

We'll start the meeting with a check-in to see how everyone is doing this week.
2. check in
Used in jails and prisons, to "check in" means to request a transfer into protective custody. Protective custody is an area within a prison or jail where security is tighter and officer presence is more pronounced. Protective custody is used mainly for rats, people with mental illness and sex offenders.
Johnny checked in the oher day after the guys in his block found out what his charges were.

We told him last week that if he didn't check in, he would be sorry that he came to our pod.
rss and gcal