lav(n = noun.artifact) bathroom, can, john, lavatory, privy, toilet - a room or building equipped with one or more toilets;
is a kind of room
has parts: can, commode, crapper, pot, potty, stool, throne, toilet
has particulars: head, comfort station, convenience, public convenience, public lavatory, public toilet, restroom, toilet facility, wash room, washroom, closet, loo, w.c., water closet

   Same as lavatory{5}; -- a shortened form of the word. [WordNet 1.5]

lav, n. Brit. colloq. lavatory.

Etymology:
abbr.