Breadcrumb Home > Dictionary > Index O oct-: Meaning and Definition of Find definitions for: oct- Pronunciation: [key] var. oforbefore a vowel: octal. Oct. Pronunciation: [key] October. oct. Pronunciation: [key] octavo. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: oct- (Thesaurus) OCS octa- ✖ Related Content Daily Word Quiz: acronym Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language