A take on the popular term "winning," it refers to identical thoughts or behavior, as well as to brilliance.
Person 1: "Oh my gosh, I was just about to say that!"
Person 2: "TWINNING!"

Person 1: "Uh, we're wearing the same sweater?"
Person 2: "TWINNING!!"
by .,.,.,.,.,. January 6, 2012
When someone and their friend say or think the same thing, they are "twinning"
Martin was twinning with his friend, Jonathan about their hobbie
by Lil Korean kiddy March 30, 2015
When you and someone else are matching clothing
Oh my god! Did you see that? They are both twinning the same prom dress!
DAMNIT!

Whats wrong billy?
NOW I CANT TELL WHICH ONE IS MORE HOT
Uh... You're 68
UH YEAH, BUT I STILL GOT SOME MILK LEFT IN ME
What the actual fuck-
by CheesyFriesWithExtraCheese October 21, 2019
The act of transforming one person into a clone of another person, examples often exist within the TG/TF fetish side of the internet.
"Have you ever seen the second and third Matrix movies? Agent Smith just goes mad and starts twinning everyone."
by Raatilam March 10, 2018
The act of Winning and being a Twin.. simultaneously.

Being Able to do anything you want exceptionally well with you're twin.

All Arguments Against TWINNERS Are Invalid
Yo man, look at will and garby dude they're always Twinning.

DUH #Twinning
by lyrically genius June 3, 2012
Doubling your sexual pleasure by getting it in with lesbian twins.
Dude 1: I got hot DTF twins comin over tonight.
Dude 2: Bro, you are so twinning!
Dude 1: Duh... Twinning!
by StattnMacy August 19, 2011