rat on someone

rat on (one)

To inform an authority figure of one's bad or illegal behavior. I can't believe you ratted on me like that to mom and dad—I'm never telling you anything ever again! The criminal ratted on his accomplices to avoid jail time.
See also: on, rat
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

rat (on someone)

in. to inform (on someone). Bill said he was going to rat on that punk.
See also: on, rat, someone
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.
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