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

I have been a know-it-all Dodger fan since the late 1950s and after last season I thought, and hoped, Clayton Kershaw would retire.

From Los Angeles Times • Sep. 20, 2025

Of course, being a kid is full of trial and error, especially when you’re a know-it-all.

From Salon • Mar. 2, 2025

They must think Hudson is a loose cannon and I’m the summer school know-it-all.

From "What If It's Us" by Becky Albertalli and Adam Silvera

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