Source : Webster's Revised Unabridged Dictionary (1913)

Piss \Piss\, v. t. & i. [OE. pissen, F. pisser; akin to It.
   pisciare, D. & G. pissen, Dan. pisse, Icel. pissa.]
   To discharge urine, to urinate. --Shak.

Piss \Piss\, n.
   Urine.

Source : WordNet®

piss
     n 1: liquid excretory product; "there was blood in his urine";
          "the child had to make water" [syn: {urine}, {pee}, {piddle},
           {weewee}, {water}]
     2: informal terms for urination; "he took a pee" [syn: {peeing},
         {pee}, {pissing}]

piss
     v : eliminate urine; "Again, the cat had made on the expensive
         rug" [syn: {make}, {urinate}, {piddle}, {puddle}, {micturate},
          {pee}, {pee-pee}, {make water}, {relieve oneself}, {take
         a leak}, {spend a penny}, {wee}, {wee-wee}, {pass water}]