rat out
B1 informal separable transitive
In simple words
To tell someone in charge about what another person has done wrong, especially when that person trusted you.
Literal meaning: Behaving like a disloyal rat — exposing others to get oneself off.
Meanings
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."
Grammar: separable
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."
Grammar: separable
Usage notes
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.
Commonly used with
friend accomplice colleague boss authorities
Forms
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
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