A very outdoorsy person, who spends most of his time out on nature walks, but then experiences a sudden burst of hornyness, so then resorts to finding the nearest bush and masturbating in it. Bush wackers generally use the closest and largest leaf to emit, or wipe up, any unwanted man goop.
Jamal: "hey Sampson! we've been hiking for hours, i say we take a break to session up some bush wacking."
Sampson: "yea dawg, im down ive a had side pipe for hours."
Jamal: "i dunno about you but ive been eyeing up that crevice in that mossy piece of bark over there"
A slang term or substitution for the meaning of somebody having sex with a girl, preferably with a large "bush".
-"Hey Jim, wana go bush wacking? I know some fine ladies"
-"I know of a few bushes we can wack, if you're interested"