Definify.com

Webster 1913 Edition

Noun.

One who knows everything; hence, one who makes pretension to great knowledge; a wiseacre; a know-it-all; – usually ironical.

[Colloq. or R.]

know -all ‎(plural know-alls)

(chiefly Britain, Ireland) Someone who obnoxiously claims to be knowledgeable on a subject.

someone who obnoxiously claims to be knowledgeable on a subject — see know-it-all