1 B1 idiomatic informal
To inform on someone to an authority, betraying their trust.
"She ratted out her classmate to the principal for cheating on the exam."
separable
rat out
B1 informal separable transitive
To inform on or betray someone to an authority, typically breaking loyalty.
In plain English
To tell someone in charge about what another person has done wrong, especially when that person trusted you.
What does "rat out" mean?
2 meanings, ordered from most common to least. Color-coded by CEFR level.
2 B1 idiomatic slang
To betray a criminal associate or partner by cooperating with law enforcement.
"One of the gang members ratted out the others to avoid prosecution."
separable
Literal vs figurative
Words literally mean
Behaving like a disloyal rat — exposing others to get oneself off.
Actually means
To tell someone in charge about what another person has done wrong, especially when that person trusted you.
Usage tip
Predominantly American English. Very similar to 'rat on' but takes a direct object more easily: 'he ratted her out' (rather than 'ratted on her'). Strong connotation of disloyalty and betrayal. Common in crime, school, and workplace contexts.
Words that pair with "rat out"
Natural word combinations native speakers use most often.
friend accomplice colleague boss authorities
How to conjugate "rat out"
The five tense forms you'll use most often.
Base
rat out
I/you/we/they
3rd person
rats out
he/she/it
Past simple
rated out
yesterday
Past participle
rated out
have + pp
-ing form
rating out
continuous
Hear "rat out" in the wild
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