/ Dictionary / Index O orthoclastic: Meaning and Definition of Find definitions for: or•tho•clas•tic Pronunciation: (ôr"thu-klas'tik), [key] — adj. Crystall. (of a crystal) having cleavages at right angles to each other. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. orthoclase ortho-cousin Related Content Daily Word Quiz: exemplary Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language