FINK
fink, snitch, snitcher, stoolpigeon, stool pigeon, stoolie, sneak, sneaker, canary
(noun) someone acting as an informer or decoy for the police
confess, squeal, fink
(verb) confess to a punishable or reprehensible deed, usually under pressure
fink, scab, rat, blackleg
(verb) take the place of work of someone on strike
Source: WordNet® 3.1
Etymology 1
Noun
fink (plural finks)
(chiefly, US, slang) A contemptible person.
(chiefly, US, slang) An informer.
(chiefly, US, slang) A strikebreaker.
Synonyms
• (informer): See informant
Verb
fink (third-person singular simple present finks, present participle finking, simple past and past participle finked)
(chiefly, US, slang) To betray a trust; to inform on.
Synonyms
• inform, grass up, snitch; See also rat out
Etymology 2
Verb
fink (third-person singular simple present , present participle fought, simple past and past participle fought)
(dialectal, th-fronting) Pronunciation spelling of think.
Etymology 3
Noun
fink (plural finks)
(South Africa) Any of several birds in the family Ploceidae native to southern Africa.
Source: Wiktionary