know-it-all

American

[noh-it-awl] / ˈnoʊ ɪtˌɔl /

noun

a person who acts as though they know everything and who dismisses the opinions, comments, or suggestions of others.

adjective

of or characteristic of a person who acts as though they know everything and who dismisses the opinions, comments, or suggestions of others.

know it all Idioms

see know all the answers.

Etymology

Origin of know-it-all

First recorded in 1930–35

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

Volker Beck, president of the German-Israeli Society, labelled Steinmeier's comments on the war "grossly inappropriate" and said they displayed a "smug know-it-all attitude".

From Barron's • Mar. 24, 2026

I offered that information with an apology, since nobody wants to come off as a know-it-all; however, matching shows with the right streaming service is part of a TV critic’s job these days.

From Salon • Dec. 10, 2025

The idea was to put to rest any worry that she might parade in like a know-it-all.

From The Wall Street Journal • Oct. 30, 2025

He paused and replied, “If we’d been less know-it-all, less ‘we’re from Harvard, so we know how to run your country and you don’t,’ do I think our relations could have developed differently?

From Slate • Dec. 23, 2024

Even though Shirley Boon, with her big know-it-all smile, kind a irritate me.

From "The Help" by Kathryn Stockett

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023