Meaning of Neptunian

Nep•tu•ni•an

Pronunciation: (nep-t'nē-un, -ty'-), [key]
— adj.
  1. pertaining to Neptune or the sea.
  2. pertaining to the planet Neptune.
  3. (often l.c.)formed by the action of water.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.