Definition of styrofoam in US English:

styrofoam

noun

trademark
  • A kind of expanded polystyrene.

    • ‘It's really not recommended to use styrofoam in the microwave.’
    • ‘However, plastic and styrofoam must be separated from the rest of the garbage.’
    • ‘The piece of styrofoam washing up to shore contrasts starkly with the shellfish pushing through the sand a centimetre beneath the surface.’
    • ‘It is a padding the color of cardboard and the consistency of styrofoam.’
    • ‘Popsicle sticks are still in vogue, as are styrofoam, garden hose tubing, particle board, wire and glitter glue.’

Origin

1950s: from polystyrene + foam.

Pronunciation

styrofoam

/ˈstīrəˌfōm//ˈstaɪrəˌfoʊm/