/ Dictionary / Index O operon: Meaning and Definition of Find definitions for: op•er•on Pronunciation: (op'u-ron"), [key] — n. Genetics. a set of two or more adjacent cistrons whose transcription is under the coordinated control of a promoter, an operator, and a regulator gene. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: operon (Thesaurus) operetta operose Related Content Daily Word Quiz: mongrel Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language