/ Dictionary / Index P polyisobutylene: Meaning and Definition of Find definitions for: pol•y•i•so•bu•tyl•ene Pronunciation: (pol"ē-ī"su-byt'l-ēn"), [key] — n. Chem. a polymer of isobutylene, used chiefly in the manufacture of synthetic rubber. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. polyimide polyisoprene Related Content Daily Word Quiz: lunar Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language