A metaphorical term for what happens when a person's rage builds up enough (in this case, creating a "vat of rage") that it can be considered to be "boiling lava hot." The "rage juice" is then unleashed upon the unfortunate foe, the heat of which causes him or her to have been burned.
If rage bukkake is considered by the receiver to be kinky, then perhaps some angry terrorism reacharound is in order.
Ralph thought he was totally owning Jenn until she snapped and unleashed her ragebukkake all over him.
When after being knocked out of the Junior Cliburn PianoComp. (esp. after preliminary round), the judges bukkake failed pianists individually on stage to rapturous applause.
August: Pretty tough crowd at the Cliburn this year!
Roger: Yeah, I didn't make it past the preliminaries, and ended up getting bukkakerogered.