/ Dictionary / Index O opto-: Meaning and Definition of Find definitions for: opto- Pronunciation: [key] a combining form meaning “optic” or “vision,” used in the formation of compound words: optometry. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. optionee optoelectronics Related Content Daily Word Quiz: diligent Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language