Source : Webster's Revised Unabridged Dictionary (1913)

Urinator \U"ri*na`tor\, n. [L., from urinari to plunge under
   water, to dive.]
   One who dives under water in search of something, as for
   pearls; a diver. [R.] --Ray.

Source : WordNet®

urinator
     n : a person who urinates [syn: {pisser}]