Yappy

to bark sharply, shrilly, or snappishly; yelp.
slang. to talk shrilly, noisily, or foolishly.
to utter by yapping.
a sharp, shrill, or snappish bark; yelp.
slang.

shrill, noisy, or foolish talk.
the mouth:
keep your yap shut.

slang. an uncouth or stupid person; b-mpkin; fool.
historical examples

doctor rabbit and brushtail the fox thomas clark hinkle
doctor rabbit and brushtail the fox thomas clark hinkle
punch, or the london charivari, vol. 153, nov. 28, 1917 various
doctor rabbit and brushtail the fox thomas clark hinkle
doctor rabbit and brushtail the fox thomas clark hinkle
doctor rabbit and brushtail the fox thomas clark hinkle

verb (intransitive) yaps, yapping, yapped
(of a dog) to bark in quick sharp bursts; yelp
(informal) to talk at length in an annoying or stupid way; jabber
noun
a high-pitched or sharp bark; yelp
(slang) annoying or stupid speech; jabber
(slang) a derogatory word for mouth
interjection
(usually reiterated) an imitation or representation of the sound of a dog yapping or people jabbering
noun
a group of four main islands in the w pacific, in the w caroline islands: administratively a district of the us trust territory of the pacific islands from 1947; became self-governing in 1979 as part of the federated states of micronesia; important j-panese naval base in world war ii. pop: 11 647 (2006 est). area: 101 sq km (39 sq miles)
adjective
usage note
adj.
v.

a stupid person; a half-wit; b–b: just a no-account yap (1894+)
a rural person; hick, yokel (1900+ hoboes)
a criminal’s victim; mark, patsy (1912+ underworld)

young aspiring professional