/ Dictionary / Index L lysine: Meaning and Definition of Find definitions for: ly•sine Pronunciation: (lī'sēn, -sin), [key] — n. Biochem. a crystalline, basic, amino acid, HN(CH)CH(NH)COOH, produced chiefly from many proteins by hydrolysis, essential in the nutrition of humans and animals. Abbr.: Lys; Symbol: K Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: lysine (Thesaurus) lysin Lysippus Related Content Daily Word Quiz: tenacious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language