a) a wild and crazy party with lots of sensuality going on, and probably some illicit substance use. cf a bash with wooing.
b) a party. a derivation from definition a)
c) an Atherton Chamber Singer's party. specialized usage, as most CS parties are woobashes(a)
It was created in and subsequently became a valid Scrabble word in Mr. Wuetcher's advanced freshman English class at Atherton High School, fall of 2001.
James' parents are gone this weekend so he's throing a woobash. Matt's getting ahold of a keg of Rolling Rock. Man, I wonder who hooks up this time.