Related formstrans-Nep·tu·ni·an, adjective
Examples from the Web for neptunian
The Neptunian leader began to gesture again, and conveyed to Burl that they wanted to attack as soon as possible.
The rocks thus deposited were called Neptunian by the older geologists.The World Before the Deluge|Louis Figuier
There was nothing to do then but to join the Neptunian assault.
It passes here, under the fanciful name of Neptunian Goblet.
Though the account is very interesting, I do not perceive its exact bearing on the Neptunian and Plutonian hypotheses.