/ Dictionary / Index L lysin: Meaning and Definition of Find definitions for: ly•sin Pronunciation: (lī'sin), [key] — n. Immunol., Biochem. an antibody causing the disintegration of erythrocytes or bacterial cells. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: lysin (Thesaurus) lysimeter lysine Related Content Daily Word Quiz: arboreal Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language