Synonyms for Fink (same or very similar meaning)
WordNet sense 1 (someone acting as an informer or decoy for the police):
canary, sneaker, snitch, sneak, snitcher, stoolie, stoolpigeon, stool pigeonWordNet sense 2 (take the place of work of someone on strike):
rat, scab, blacklegWordNet sense 3 (confess to a punishable or reprehensible deed, usually under pressure):
confess, shrive, squealFrom the ODE community, based on WordNetadd/edit