a lightweight, transparent, thermoplastic synthetic resin, used for aircraft canopies, lenses and windows, etc.
noun
this material
See Plexiglas in American Heritage Dictionary 4
(plĕkˈsĭ-glăsˌ)
A trademark used for a light, transparent, weather-resistant thermoplastic. This trademark also occurs in many instances lowercased and spelled plexiglass: “The display pieces are double sealed inside plexiglass cases”(Los Angeles Times).