From WordNet (r) 3.0 (2006) [wn]:
relieve oneself
v 1: eliminate urine; "Again, the cat had made on the expensive
rug" [syn: make, urinate, piddle, puddle,
micturate, piss, pee, pee-pee, make water,
relieve oneself, take a leak, spend a penny, wee,
wee-wee, pass water]