/ Dictionary / Index S spermidine: Meaning and Definition of Find definitions for: sper•mi•dine Pronunciation: (spûr'mi-dēn", -din), [key] — n. Biochem. a biogenic polyamine, HN(CH)NH(CH)NH, formed from putrescine, occurring widely in nature and first identified in semen. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. spermicide spermine Related Content Daily Word Quiz: nefarious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language