1. pertaining to speech.
(a) [mid-19C+] (US, also yapper, yop) the mouth, usu. in derog. sense, e.g. shut your yap! etc.
(b) [mid-19C+] (orig. US, also yop) idle, trivial chatter; an act of speaking (see cit. 1940).
(c) [20C+] (Irish, also yerp) a whining, complaining person.
(d) [20C+] (US, also yapper, yap yap) a chatterer.
(e) [1910s–20s] (US, also yapper) a tell-tale, an informer.
(f) [1920s–50s] a sound.
(g) [1950s+] (orig. US) a chat, a conversation.
(h) [1980s] a petty swindler.
2. fig., derog. uses .
(a) [late 19C–1940s] (US, also yappo) a contemptible person, irrespective of class or background.
(b) [late 19C+] (US, also yawp) a derog. term for a peasant, a rustic simpleton.
(c) (also yap-yap) attrib. use of sense 2b.
(d) [20C+] (US Und.) a criminal’s victim.
(e) [1920s] (US tramp) a novice within the hobo community.
a night club.
[1920s] (US) a rustic.
[1920s] (US) a vehicle taking tourists on sightseeing tours.
[1950s] (US) to be quiet.
see shoot off one’s mouth under shoot off v.
see zip one’s lip v.