The Collaborative International Dictionary of English v.0.48:

Polyurethane \Pol"y*ur`eth*ane\, n. (Chem.)
   any polymer containing [-NH.CO.O-] linkages; such polymers
   are much used as the basis of light but rigid foams for
   packaging (

   polyurethane foam) and for hard coatings, as on floors.
      [PJC]

WordNet (r) 3.0 (2006):

polyurethane foam
    n 1: a foam made by adding water to polyurethane plastics [syn:
         polyfoam, polyurethane foam]