An onomatopoetic phrase
stated out loud when one has a boner.
Typically, the second 'bump' is stated with higher
inflection, and the volume of the phrase is
representative on how raging the boner is.
The phrase can also be used in general situations of extreme happiness.
After seeing a
tall blonde girl with huge tits walk past you while sitting on the park bench with a couple of buddies: "bump bump"
"Hey bro, I just saw that hot
ging at that party, and I totally bump
bumped."
"Tiger Woods just won the tournament, our douchebag varsity golf roommate Patrick probably just bump bumped."