/ Dictionary / Index I isoleucine: Meaning and Definition of Find definitions for: i•so•leu•cine Pronunciation: (ī"su-l'sēn, -sin), [key] — n. Biochem. a crystalline amino acid, CHO, occurring in proteins, that is essential to the nutrition of humans and animals. Abbr.: Ile; Symbol: I Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: isoleucine (Thesaurus) Isolette isoline Related Content Daily Word Quiz: penury Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language