Any relationship between creatures of the same sex, up to the point that balls do not touch. After this things turn gay.
Bromancer 1: Love is love...
Bromancer 2: Bromance is FOREVER!
I enjoy a nice paddle up the river when it floods, such bromancing opportunities are priceless.
Benny(gay):Hey Marley, lets go have a nice DM in those bushes over there?
Marley(bromancer): *gets the hell outta there* maybe another time Benny...
Lancey(bromancer): Hey Tez, your ass is looking so sexy today.
Tez(bromancer): Thanks Lance, don't get too close now ya hear? Lets keep things low-grade bromantic pls. You know I'm not into none of that Yaranaika business!