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know-it-all
know-it-allnouna person who acts as though they know everything and who dismisses the opinions, comments, or suggestions of others.
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know it all
know it allsee know all the answers.
know-it-all
Americannoun
adjective
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
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Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.