Source : Webster's Revised Unabridged Dictionary (1913)

Plutonic \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}.

Source : WordNet®

plutonic
     adj : of igneous rock that has solidified beneath the earth's
           surface; granite or diorite or gabbro [syn: {irruptive},
            {eruptive}]