polystyrene

/ˌpɑːliˈstaɪriːn/

poly·styr·ene

BrE /ˌpɒliˈstaɪriːn/

NAmE /ˌpɑːliˈstaɪriːn/

(also Styrofoam™ especially in NAmE ) [U]

a very light soft plastic that is usually white, used especially for making containers that prevent heat loss

polystyrene cups