A know it all is someone who thinks they know everything, and refuses to take anyone else's opinion into consideration because, naturally, they know it all. Also known as a Brian.
I have green eyes but my boyfriend Brian insists that I have hazel eyes. Clearly he is a know it all.
by Arniverna September 10, 2022
Someone who goes around thinking things are big and clever, and believe they know it all about everything, but don’t because their still things he / she don’t know about just yet.
by Urbantheturban July 08, 2019
Person typically has one button and it’s their way or nothing else. Don’t disagree with a know it all because if you do your entire day will change. They will quickly flip the script and could even lead to hate crimes, or even worse the “ K bye”
by Reneman April 27, 2018
A lot of people confused the guy with a know it all. He didnt think he had all the answers to everything, but he was sure of which ones were bullshit.
by Solid Mantis June 10, 2020