slang; generically used to signify an illicit substance that cannot be procured in any ordinary means by the general public. An essential prerequisite involves an uncharacteristically underground drug dealer who conceals him/herself in little conclaves on certain un-lit side roads, selling these aforementioned illicit substances.
Hey, I saw Swathi today outside UCL. She was smoking a bit that wacky backy!
by Venkat.Thiagarajan April 21, 2010