From over 35 years of personal knowledge. . . .
Means especially large, really big, packed and mounded bong hit, specifically applied for punitive purposes, after some really dumb move or fuckup. Much, much more bigger & packed than a normal size bong hit.
(Putting aside, of course, that the result is pleasurable - yet punitive in the sense you are seriously fucked up, brain scrambled and unable to function, or even speak coherently, for awhile ; the sentence is more a reward than anything else. Possibly resulting in encouraging or reinforcing bad behavior.)
See also "PB-Penalty Bong"
“Oh wow Dude, you did NOT just…..(A) spill all the rest of our dope on the floor? (B) tell your Mom we just dropped acid? (a personal best – fuck, another PB!) (C) pee yourself? (D) tell that cop we were stoned? (E) smoke all that joint without givin’ me a hit? (F) eat all the rest of the chocolate chip cookies? (G) spill the bong water? (H) do your girlfriends Mom and not invite me? . . . penalty bong!”
(and in REALLY bad instances it was referred to as
"Penalty Fuckin Bong or P Fuckin B")