Neptunian

a. [Fr. neptunien, from Lat. Neptunius, belonging to Neptune.] 1. Pertaining to the ocean or sea. 2. Formed by water or aqueous solution; as, Neptunian rocks.

Neptunian theory (Geol.), the theory of Werner, which refers the formation of all rocks and strata to the agency of water;—opposed to the plutonic theory.

n. [Fr. neptunien, neptuniste. See Népt'ū-nist, supra.] One who adopts the theory that the whole earth was once covered with water, or rather that the substances of the globe were formed from aqueous solution.