Quite similar to "busting nut" it refers to ejaculating, or "Busting Ghost". Derived from people saying, "oh we were just alone watching Ghost Busters," and friends responding, "what? were you two busting ghost."
looking for crack, coke, or speed on the ground because you're so spun out you KNOW you dropped some and look there's a fleck of white ... oh I lost it THERE IT IS
Dude was crazy, lookin' at the ground, pickin' up gravel, old crackheads ghost bustin'