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

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

Throughout the season Tuck strikes a wonderful balance between Kevin’s know-it-all enthusiasm and the internal bruising he carries due to his inability to fit in.

From Salon • Jul. 24, 2024

I bet she can’t wait to get back to her know-it-all friends and tell them how Jane McKeene is a mad half-wit that believes in invisible creatures swimming around in our blood.

From "Dread Nation" by Justina Ireland

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