- For Teachers
In a classroom for example, than when somebody is cheating and a classmate told the teacher the misdeed.
* What do you call the thing that the classmate did?
* What do you call the classmate?
I suppose you can say he snitches on the culprit or he sneaks on the culprit.
Jack called Ana a rat when he discovered that she has been snitching/sneaking on her classmates.