Calling someone "That Guy" is saying that they would obviously be the one that would do a particular thing. This reference can only be made after the event has happened.
Person 1: Dude I'm so sorry but I just clogged your toilet again.

Person 2: Wow... You would be That Guy that clogs my toilet more than once.
by Ike Nwamgbe September 29, 2011
THAT GUY is the person who comes to your party gets completely wasted, passes out, pisses, and pukes all over themselves and your carpet; wakes up before anyone else and leaves without cleaning it up.
no example needed to explain this scenerio of THAT GUY
by The Legacy December 8, 2005
He fools you once, you're mad. Fools you twice, how could he. Fools you three times and he's officially that guy, you know the one. He goes to the bar and he's like "This suit is officially Georgio Armani, my dad knows him", FUCK YOU. I AAAAAIIIIINN'T HAVIN THAT SHIT!
by Unknowni123 July 30, 2013
A person in the background that draw attention from the main subject
Look at "that guy" in the background of this picture grabbing his balls
by J- sus January 9, 2006
Someone who goes for younger girls, most often occurs with a large age difference, Someone who is just known to be that guy.
Dylan: Who's that guy who's always creeping on the grade 9's.

Lachlan: Thats me, Im that guy.
by y.m.c.m.b February 26, 2011
That Guy is the baddest motherfucker on this earth, you can usually hear about him in tv shows when the main characters are jealous because "That Guy's getting laid by those two gals tonight" or "That Guy actually bought Playboy Mansion".

An easy mistake to make is hear about "that guy" and believe people are referring to "That Guy". The two are polar opposites, one being the pinnacle of awesome and the other being a retarded pussy that frequent parties orchestrated by 15 year olds.

While That Guy is pretty cool, he's also an elitist asshole, so you're probably not his friend unless you're easy and pretty hot, in which case you're not reading this.
-"That Guy just made it with her"
-"What? But she's my (trophy) wife!"
-"Apparently That Guy doesn't care much for the bonds of marriage"
-"Neither do I but I'm an old rich man!"
-"I hear your wife's on redtube now"

That Guy taking from the rich and giving back to the poor.
by Metal308 October 3, 2009
(n.) A male notorious for his artistry in seducing the fairer sex.
Katie, despite her adamant claims, was beguiled when she met that guy beneath heaven's starry canvas.
by theFlannelVillain June 18, 2010