A sudden burst of strenght and invinceablility. Made famous by the god of wrestling, "The Immortal" Hulk Hogan.
"By God, he's Hulking up" Jim Ross said, "Hulk Hogan has hulked up against the Rock!"
This is the act of your penis going into a blind rage and like the Hulk attempts to take down all in it's sight.
This chick with a huge ass walked by and I just started "Hulking Up" on her.