The Oxford Thesaurus An A-Z Dictionary of Synonyms - yap v.

1) bark, yelp: Their dog was yapping away all night. 2) gabble, babble, blither or blather, chatter, jabber, tattle, prattle, prate, Colloq chiefly Brit witter, natter, Slang jaw, run on, US run off at the mouth: I wish she'd stop her yapping and give me some peace. --n. 3) mouth, Slang trap, gob, US bazoo: If only Sam would shut his big yap once in a while!