A phrase said by Brazilian online players when they join a game. Roughly translates to "Anybody Brazilian?" in Portuguese, with BR being an abbreviation of Brazil.
Similar to russian players who play CS:GO, unfortunately, players who say this are known to unwittingly throw the game due to lack of communication to the other English-speaking players.
Some players (who may not be Brazilian at all) may say this to troll other players.
*Red 1 joins the game.*
Red 1: alguem br
...
...
*Red Team has lost the game!*
Red 2: Red 1! You left us wide open!
Red 1: Você não fez nada! You did not do anything!
*Blue 3 has joined the match.*
Blue 3: Alguem BR
Blue 2: Oh god, if we lose this round thanks to this idiot...
...
*Blue 3 just team-wiped the Red team!!*
Red 1: Where the hell did this guy come from!?
Blue 3: HUEHUEHUEHUEHUE HUEHEUHEUEHYUEHUE
Blue 2: You lying jerk!! D8<
A link some guy created when referring to "tldr." The fact you have clicked on this link probably means you have seen all there is to see on the Internet. Go outside, get some exercise.