It is duel purpose term that can be used to express a mans gayness or a woman's sluttiness. Essentially you pointing out that that person has sex with an abundance of men.
Jake: Look at those guys holding hands...
Mike: Fuckin dudebangers.
Sam: I slept with jenny last night.
James: That's not much of an accomplishment seeing as how she's a dudebanger and all...
One who has sex with dudes and/or gets penetrated repeatedly by dudes.
"That flamboyant person has got to be a dudebanger"
"Christina is a dudebanger for sure."