/ Dictionary / Index I isooctane: Meaning and Definition of Find definitions for: i•so•oc•tane Pronunciation: (ī"sō-ok'tān), [key] — n. Chem. the octane CH, used as one of the standards in establishing the octane number of a fuel. Cf. octane number. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Isonzo iso-osmotic Related Content Daily Word Quiz: stringent Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language