Breadcrumb Home > Dictionary > Index F feldspar: Meaning and Definition of Find definitions for: feld•spar Pronunciation: (feld'spär", fel'-), [key] — n. any of a group of minerals, principally aluminosilicates of potassium, sodium, and calcium, characterized by two cleavages at nearly right angles: one of the most important constituents of igneous rocks. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: feldspar (Thesaurus) Feldene feldspathic ✖ Related Content Daily Word Quiz: musth Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language