know-it-all

[ noh-it-awl ]

/ ˈnoʊ ɪtˌɔl /

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

of or characteristic of a know-it-all.

Origin of know-it-all

First recorded in 1930–35

He made an easy target, the know-it-all liberal egghead who demeaned the wisdom of the American people.

Obamacare Architect: I Wanted to Sound Smart |Ben Jacobs |December 9, 2014 |DAILY BEAST
He was kind of a know-it-all, talked with a lot of authority on different subjects.

Whitey Bulger’s Women: Inside the Terror and Glamour of His Ex-Girlfriends |T.J. English |June 11, 2012 |DAILY BEAST
The reader can rest assured that behind all the blood and viscera is a know-it-all having some fun.

Must Read Fiction: ‘Prague Fatale,’ ‘Derby Day’ and More |Malcolm Forbes, Hillary Kelly, Mythili Rao |May 9, 2012 |DAILY BEAST
He can still come off like a windbag with a know-it-all air.

The Resurrection of Newt Gingrich |Howard Kurtz |October 18, 2011 |DAILY BEAST

His whole life is models, gold leaf and marble columns, but he still sounds like a know-it-all down at the OTB.

Obama Roasts Trump |Lloyd Grove |May 1, 2011 |DAILY BEAST
None of the new girls appeared to be inclined toward a “know-it-all” attitude, for which Jane was grateful.

Jane Stewardess of the Air Lines |Ruthe S. Wheeler
"She is—and she's just what you need," said Sue, with that know-it-all smile of hers.

The Harbor |Ernest Poole
"I've a good mind not to tell you, Mr. Know-it-all," exclaimed Johnny Chuck.

The Adventures of Reddy Fox |Thornton W. Burgess
He is impressed with the suggestion that the speaker is a "know-it-all" fellow.

Certain Success |Norval A. Hawkins
He must keep in sympathetic touch with the new, damning the know-it-all frame of mind.

The Conquest of Fear |Basil King