look up any word, like blumpkin:
 
1.
If you catch someone doing an action they are not supposed to be doing and you tell someone else to get them in trouble.

Telling on a person when they have done something they are not supposed to do.

To tell on someone.
A boy is about to take $10 from his mother's purse. His sister walks in and says, "If you take mom's money I'm going to blow you in!"
by Ruby Crystal Diamond July 20, 2011