/ Dictionary / Index P periclase: Meaning and Definition of Find definitions for: per•i•clase Pronunciation: (per'i-klās", -klāz"), [key] — n. a cubic mineral, native magnesia, MgO, occurring usually in metamorphosed dolomite. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: periclase (Thesaurus) perichondrium Periclean Related Content Daily Word Quiz: secular Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language