Knowone 

When an idiot spells “no one” incorrectly.

Brad: Dude… knowone cares
Steve: you can’t even spell bro

Knowone by Sunnybrooke December 11, 2021

it takes one to know one 

This means that no one is better at finding a wrongdoer than another wrongdoer. So if you do something wrong, then you would know if someone else followed your mistake, or you would know someone with the same quality as yourself, did the same mistake if that makes any sense lmao. The example will help better your understanding.

Zack: You are a two faced bitch!
Clay: It takes one to know one.

it takes one to know one by GrammarQueen August 23, 2017

Takes One To Know One

The worst and most pathetic comeback in the world.

"You're a whore."
"Takes one to know one!"
"That doesn't change the fact that you spread your legs for money."

Takes One To Know One by Treeeees January 25, 2010

knowoverload 

verb noh-ver-lohd; noun noh-ver-lohd

verb (used with object)
to load knowledge with excess; I studied so much I can’t remember anything.

noun
an excessive amount of learning.

I studied so much I can’t remember anything, I'm knowoverloaded.

knowoverload by therobbi May 3, 2023

know one's stuff 

To be a master of something, to be competitive in a particular field

Urban Dictionary knows its stuff in slang words definitions (neutrum form of "know one's stuff")

know one's stuff by TomPigeon January 15, 2014

Knowner

A new-age cocktail of "known" and "owner".

Ted is a knowner of a fusey.

Knowner by blufffo April 28, 2015

know one's onions 

to be competent and authoritative in one's work

He really knows his onions when it comes distilling alcohol.(example of know one's onions)

know one's onions by The Return of Light Joker October 18, 2010