Plutonic

Part of speech: adjective (a.)

1. Of or pertaining to Pluto; Plutonian; hence, pertaining to the interior of the earth; subterranean.

2. Of, pertaining to, or designating, the system of the Plutonists; igneous; as, the Plutonic theory. Plutonic action (Geol.), the influence of volcanic heat and other subterranean forces under pressure. -- Plutonic rocks (Geol.), granite, porphyry, and some other igneous rocks, supposed to have consolidated from a melted state at a great depth from the surface. Cf. Intrusive rocks, under Intrusive. -- Plutonic theory. (Geol.) See Plutonism.