A bro who encourages/motivates another bro.
Bro1: Bro, think I can do this?
Bro2 (brotivator): You got this bro!
A bro that motivates other bros to perform brotherly deeds.
Bro 1: "Go help that bro put that decal on the back of his truck."
Bro 2:"Yeah brotillery. I definitely should. You're such a brotivator!"