polymerized propylene, a very light, highly resistant, thermoplastic resin used to make coatings, plastic pipe, packaging material, fibers for clothing fabrics, etc.
See polypropylene in American Heritage Dictionary 4
(pŏlˌē-prōˈpə-lēnˌ)
noun
Any of various thermoplastic resins that are polymers of propylene. They are hard and tough, and are used to make molded articles and fibers.