/ Dictionary / Index P polyisoprene: Meaning and Definition of Find definitions for: pol•y•i•so•prene Pronunciation: (pol"ē-ī'su-prēn"), [key] — n. Chem. a thermoplastic polymer, (CH), the major constituent of natural rubber and also obtained synthetically. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. polyisobutylene polymath Related Content Daily Word Quiz: rustic Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language