[pol-ee-stahy-reen, -steer-een]
noun Chemistry.
a clear plastic or stiff foam, a polymer of styrene, used chiefly as an insulator in refrigerators and air conditioners.

1925–30; poly- + styrene

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World English Dictionary
polystyrene (ˌpɒlɪˈstaɪriːn)
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

Collins English Dictionary - Complete & Unabridged 10th Edition
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Word Origin & History

1927, so called because it is a polymer of styrene (see styrene).
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Science Dictionary
polystyrene   (pŏl'ē-stī'rēn)  Pronunciation Key 
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.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Britannica


an important member of the class of synthetic organic polymers, composed of long-chain molecules prepared by a chemical reaction in which many (usually 2,000-3,000) molecules of the aromatic hydrocarbon styrene become linked together.

Learn more about polystyrene with a free trial on Britannica.com.

Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
The walls were lined with aged polystyrene foam blocks for insulation.
They started with a collection of spherical polystyrene pellets.
They're space efficient too: a one-inch-thick ash panel equals today's
  four-inch-thick polystyrene panels.
Anglers often use a piece of a milk jug, polystyrene foam, chopped-up swimming
  noodles and other plastic chunks.
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