Plu‐ton″ic (?), a. [Cf. F. plutonique. See Pluto.] 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.