/ Dictionary / Index O optical isomer: Meaning and Definition of Find definitions for: op'tical i'somer Pronunciation: [key] — Chem. Chem. any of two or more isomers exhibiting optical isomerism. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. optical illusion optical isomerism Related Content Daily Word Quiz: loathe Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language