The Collaborative International Dictionary of English v.0.48:

Pee \Pee\, n.
   1. (Naut.) Bill of an anchor. See Peak, 3
      (c) .
          [1913 Webster]

   2. Urine.
      [PJC]

   3. The act of urinating; -- used in the informal

   take a pee, meaning, to urinate.
      [PJC]