A place where stoners, taggers, and hobos hang out at. The word "wash" comes from a slang term meaning drain wash, or the sewer. The Wash usually refers to the ones with a tunnel where they can do they thang.
Stoner: Yo man we're hittin' up The Wash a little later to hit Stony's new pipe.
Tagger: Aye mayne we postin' up at The Wash downtown tonight, you down?
Hobo: Stop thrown' rocks at my tent you crazy teenagers!!!