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.

But it’s voters who decide elections, not know-it-all columnists.

From Los Angeles Times • Jun. 7, 2026

In a 2015 biography, author Ashlee Vance described Musk as "a confrontational know-it-all" with an "abundant ego".

From BBC • Jun. 4, 2026

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

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

Roland Mathers, who is kind of a know-it-all and talks like he’s forty, raises his hand and starts to speak even before she calls on him.

From "Finding Junie Kim" by Ellen Oh

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