snitch

(noun) someone acting as an informer or decoy for the police. Synonyms: fink, snitcher, stoolpigeon, stool pigeon, stoolie, sneak, sneaker, canary.

(verb) take by theft. Synonyms: hook, thieve, cop, knock off, glom. Example: "Someone snitched my wallet!."

(verb) give away information about somebody. Synonyms: denounce, tell on, betray, give away, rat, grass, shit, shop, stag. Example: "He told on his classmate who had cheated on the exam."