When two bromates take a shower at the same time (in neighboring shower stalls). Browers are usually characterized by an ongoing conversation between the bromates and typically occur in an advanced bromance.
Bromate 1: Dude, I think one of my balls is bigger than the other.
Bromate 2: Yeah I know. You told me last night during our brower.
Bromate 1: Oh, no shit?
Bromate 2: No shit, bro.