rat out

Inform on someone

To rat out someone is to inform on them, typically to an authority: He ratted out his partners to the feds.

The phrase carries strong connotations of betrayal—rats abandon sinking ships, and a rat is slang for an informer.

The out emphasizes exposure: secrets brought into the open.

informing

snitch

One who tells authorities

tattleReveal another's wrongdoing
squealShrill, piercing cry
whistleblowerInsider who reports misconduct

informant · informer · tipster · leak · tip-off · report · testify · witness · expose · reveal

slang

snitch

One who tells authorities

grassNarrow-leaved ground cover
narkPolice tipster, slang
narcUndercover drug officer

fink · stoolie · squealer · canary · stool pigeon · blabbermouth · telltale · tattletale · dobber · supergrass

betrayal

traitor

One who betrays allegiance

turncoatOne who betrays allegiance
backstabberDisloyal pretend ally
selloutCompromiser of integrity

betrayer · double-cross · treachery · disloyalty · Judas · fink · perfidy · treason · two-faced · sneak

Categories

accusationsaccusation, accuse, accuser, allegation, allege
betrayalbackstab, betray, betrayal, traitor, backstabber
dirty tacticsdirty trick, dirty tricks, dirty pool, foul play, cheap shot
underworld slangsnitch, hitman, capo, consigliere, omerta
Informerssnitch, informer, informant, fink, squealer
disclosurerevealing, disclosing, disclosure, disclose, divulge

Opposites

disclosure of secrets/betrayal

rat outkeep quiet

Remain silent

keep mum · cover up · keep one's mouth shut · hold one's tongue · say nothing

loyalty and allegiance

rat outprotect

Keep from harm

shield · cover for · stand by · have someone's back · stick up for

Family

rat, rats, ratted, ratting, ratter

Familiarity: Top 100,000
Profile: Known to kids · Used worldwide · Timeless · Negative · Everyday, not technical · Rated G