polystyrene

American  

[pol-ee-stahy-reen, -steer-een] / ˌpɒl iˈstaɪ rin, -ˈstɪər in /

noun

Chemistry.

1. a clear plastic or stiff foam, a polymer of styrene, used chiefly as an insulator in refrigerators and air conditioners.

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polystyrene British  

/ ˌpɒlɪˈstaɪriːn /

noun

1. a synthetic thermoplastic material obtained by polymerizing styrene; used as a white rigid foam ( expanded polystyrene ) for insulating and packing and as a glasslike material in light fittings and water tanks

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polystyrene Scientific  

/ pŏl′ē-stī′rēn /

1. A brittle synthetic polymer composed of repeated styrene units. Polystyrene is transparent and rigid because the benzene rings in each styrene unit prevent the polystyrene chains from arranging themselves into a tight crystalline structure. Polystyrene has a wide variety of uses, especially as a solid foam for insulation and packaging.

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Etymology

Origin of polystyrene

First recorded in 1925–30; poly- + styrene

Compare meaning

How does polystyrene compare to similar and commonly confused words? Explore the most common comparisons:

• polystyrene vs. Styrofoam

Example Sentences

The Harlands, who built the structure using polystyrene packaging acquired from a friend, said that they were inspired by a similar display they saw on a holiday in Ghent, Belgium.

From BBC • Apr. 12, 2026

Wilson believes that Snow Secure—the high-tech insulated polystyrene blanket that unfolds like an accordion, then drapes over a pile of snow—is just the invention.

From Slate • Apr. 11, 2026

"Common plastics include polyethylene, polypropylene, polystyrene and polyethylene terephthalate or PET. The majority of these microplastics are cleared from our bodies, however studies show they do accumulate in our organs, including our brains."

From Science Daily • Mar. 13, 2026

Dell pointed to SB 54’s de facto ban on polystyrene, which went into effect on Jan. 1, 2025.

From Los Angeles Times • Feb. 27, 2026

Dry little pellets of snow, like tiny spheres of polystyrene, chased around in swirls.

From "A Walk in the Woods" by Bill Bryson