[ploot-n-iz-uh m]
noun Geology.
  1. the intrusion of magma and associated deep-seated processes within the earth's crust.
  2. (often initial capital letter) the disproven theory that all rocks formed by solidification of a molten mass, promulgated by Scottish geologist James Hutton (1726–97).

Origin of plutonism

First recorded in 1840–50; pluton(ic) + -ism
Related formsplu·to·nist, noun Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018