Much like a broseph, a brobarian is equal to that of a bro, dude, man, etc. with the defining characteristics of being a rather large individual, usually quite muscular and strong, and being the friend that typically starts/finishes fights.
Jason: Dude, I wouldn't mess with Patrick if I were you, he's a fucking brobarian of mine.
Andy: Yeah, and what if I do mess with him?
PATRICK: I WILL FUCKING CRUSH YOUR FACE AND BEAT YOU WITH MY 5 IRON.