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1.
A phrase trolls use to piss off an already mad person even more.
Person 1:WTF THIS IS THE DUMBEST SHIT THREAD EVER HOLY SHIT OMG IM SO FUCKING MAD IM GOING TO KILL YOU ALL!!!!1!!

Person 2:lol U mad bro?

Person 1: FFFFFFUUUUUUUUUUUUUUUUUUUUUUUUU
by xcdemon05 September 12, 2010
 
2.
Phrase commonly used by internet trolls when the slightest bit of anger or rage is detected (Much like sharks catching the smell of blood). Is known to drive even the sanest person to boiling rage.
Troll: Why do they call it an Xbox 360? Because when you see it you do a 360 degree turn and walk away
Noob: 360 means you face back at it, noob.
Troll: no it dont lul
Noob: wtf yes it does go back to 3rd grade
Troll: umadbro?
Noob: FFFFFFFFFFFFFFFFFUUUUUUUUUUUUUUUUUU
by Rayge April 14, 2010
 
3.
A great way to make a mad bro even madder. Used when anger is obvious, to trigger rage for personal amusement.
Random Drunk Guy: Who the f**k do you think you are dancing with my girl
Awesome Guy: Umad bro?
Random Drunk Guy: IMMA F**KN ...
by Makro3922 November 17, 2010
 
4.
A phrase commonly used in games in which one player is intentionally doing something in order to piss another off. This phrase is then repeated multiple times as a way of pissing off the offended player, causing them to want to reach through their screen and strangle the 10 year old kid on the other side and leaving the occasional gaping hole in one's computer, TV, etc. screen.
Offended: Dude, leave me alone.
Offending: U Mad Bro?
Offended: Seriously, leave me alone!
Offending: U Mad Bro?
Offended: Dude!
Offending: U Mad Bro? U Mad Bro? U Mad Bro?
Offended: GODDAMMIT!.
by BigFish April 02, 2013
 
5.
Usually used when referencing someone who is extremely angry in a post or online game chat area.
Calm down, umadbro?
by Saavix March 30, 2011
 
6.
When Your friend starts hating on you, and you commonly say ''Umad bro?"
When a friend gets jealous of you its obvious but you say umad bro.
by GWS Gang December 09, 2011
 
7.
A phrase previously used by trolls, but now used by 12 year old's trying to be cool.

Was used on the image board 4chan.

But now spread around Youtube and Runescape by fucking conformists. Thus making this phrase the most annoying piece of shit ever to come onto the internets.

Seriously, it's even worse than 'coolstorybro'
Jim: You're an ass hole

12y.oconformist: "umadbro"

Mature people: Fucking egg in a bun.
by Vope February 28, 2011