Acronym for Super MotherFucking Weak Ass Shit (S.M.F.W.A.S). Pronounced Smiff-was.
Adjective, describes anything that is weak in nature and deemed to be pathetic, whether it be a choice someone makes or someone who is scrawny and needs to hit the weights.
Originated as W.A.S. but then the S.M.F. was added to imply even more weakness.