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 of know-it-all

First recorded in 1930–35
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for know-it-all