Someone acting as an informer or decoy for the police.

synonyms: canary, fink, sneak, sneaker, snitcher, stool pigeon, stoolie, stoolpigeon.

Roget 529: disclosure; retection^†; unveiling etc. v.; deterration^†, revealment, revelation; exposition, exposure; expose; whole truth; telltale etc. (news) 532.    acknowledgment, avowal; confession, confessional; shrift.    bursting of a bubble; denouement.    [person who discloses a secret] tattletale, snitch, fink, stool pigeon, canary.    ... show more

Take by theft:
— Someone snitched my wallet!.

synonyms: cop, glom, hook, knock off, thieve.

Dutch: stelen

Give away information about somebody.

synonyms: betray, denounce, give away, grass, rat, shit, shop, stag, tell on.

Roget 529: disclose, discover, dismask^†; draw the veil, draw aside the veil, lift the veil, raise the veil, lift up the veil, remove the veil, tear aside the veil, tear the curtain; unmask, unveil, unfold, uncover, unseal, unkennel; take off the seal, break the seal; lay open, lay bare; expose; open, open up; bare, bring to light.    divulge, reveal, break; squeal [Coll.], tattle [Coll.], sing [Coll.], rat [Coll.], snitch [Coll.]; let into the secret; reveal the secrets of the prison house; tell etc. (inform) 527; breathe, utter, blab, peach; let out, let fall, let drop, let slip, spill the beans, let the cat out of the bag; betray; tell tales, come out of school; come out with; give vent, give utterance to; open the lips, blurt out, vent, whisper about; speak out etc. (make manifest) 525; make public etc. 531; unriddle etc. (find out) 480.1; split.    acknowledge, allow, concede, grant, admit, own, own up to, confess, avow, throw off all disguise, turn inside out, make a clean breast; show one's hand, show one's cards; unburden one's mind, disburden one's mind, disburden one's conscience, disburden one's heart; open one's mind, lay bare one's mind, tell a piece of one's mind [Fr.]; unbosom oneself, own to the soft impeachment; say the truth, speak the truth; turn King's evidence, Queen's evidence; acknowledge the corn [U.S.].    raise the mask, drop the mask, lift the mask, remove the mask, throw off the mask; expose; lay open; undeceive^†, unbeguile^†; disabuse, set right, correct, open the eyes of; d_esillusionner.    be disclosed &c.; transpire, come to light; come in sight etc. (be visible) 446; become known, escape the lips; come out, ooze out, creep out, leak out, peep out, crop-out; show its face, show its colors; discover itself &c.; break through the clouds, flash on the mind.    ... show more

Dutch: misleiden, aangeven, verklikken, bedriegen, verklappen, verlullen, verraden