/ Dictionary / Index A anorthosite: Meaning and Definition of Find definitions for: an•or•tho•site Pronunciation: (an-ôr'thu-sīt"), [key] — n. Petrol. a granular plutonic rock composed largely of labradorite or a more calcic feldspar. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. anorthoclase anoscope Related Content Daily Word Quiz: fervor Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language