What does it mean to “squeal on someone”

Question

What does it mean?

He can't squeal on him.

Answer 1

From American Heritage Dictionary via Wordnik:

squeal Slang To turn informer; betray an accomplice or secret.

Here's some synonyms from The New Oxford American:

inform on, tell tales on; report, give away, be disloyal to, sell out, stab in the back; informal rat on, rat out, snitch on, put the finger on, finger, sell down the river.

You can find some good examples of it in use at Wordnik.

Answer 2

It started off as criminal argot, but has worked its way into the general vocabulary to mean anyone who "tells" on someone for doing something "wrong". A sister can squeal on her broother, a student can squeal on another student, and so on.

Answer 3

"Squealing on someone" is a colloquial expression meaning to inform the police of someone's illegal activities.