snitch

verb

To secretly inform an authority about someone's wrongdoing or a secret.

"He snitched on his brother for breaking the vase."

noun

A person who secretly informs an authority about others' misdeeds or secrets.

"Nobody likes a snitch in the classroom."

Thesaurus

Synonyms: fink, sneaker, canary, stoolie, stoolpigeon, stool pigeon, sneak, snitcher, knock off, thieve, glom, cop