/ Dictionary / Index O optic axis: Meaning and Definition of Find definitions for: op'tic ax'is Pronunciation: [key] — Crystall. Crystall. (in a crystal exhibiting double refraction) the direction or directions, uniaxial or biaxial, respectively, along which this phenomenon does not occur. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. optical wedge optic center Related Content Daily Word Quiz: impetuous Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language