Source : Webster's Revised Unabridged Dictionary (1913)

Oceanus \O*ce"a*nus\, n. [L., from Gr. ?.] (Gr.Myth.)
   The god of the great outer sea, or the river which was
   believed to flow around the whole earth.

Source : WordNet®

Oceanus
     n : (Greek mythology) god of the stream that flowed around the
         earth in ancient mythology