know-it-all

[noh-it-awl] /ˈnoʊ ɪtˌɔl/

noun

a person who acts as though he or she knows everything and who dismisses the opinions, comments, or suggestions of others.

adjective

of or characteristic of a know-it-all.

Origin

1930-35

Examples from the web for know-it-all

Today, new employees arrive on their first day with an alarming amount of know-it-all.
But all of a sudden, she's a know-it-all who can explain everything.

Slang definitions & phrases for know-it-all

noun

A person who pretends to virtual omniscience; bigmouth, smart-ass: Just what we need around here, another know-it-all (1895+)