One who practices butthole surfing - the act of intravenously injecting an aqueous solution of both
LSD and
heroin (or another interchangably potent opioid analgesic). The author strongly discourages this kind of behavior, being considerably more risky than IV self-administration of either compound independently, which is saying alot.
The name was of course also adopted by the well known Texan acid-punk
band the Butthole Surfers.