A trademark name (often used generically) for fiberglass; a composite material made from glass fibers embedded in resin, used in boats, cars, and building panels.
Compound of 'fiber' and 'glass,' originally a trademark by Owens Corning in the 1930s; now often used as a generic term for fiberglass products.
Fiberglas (one 's') started as a trademark that became so useful everyone just started calling all fiberglass by that name. It's like how people say 'Kleenex' for tissues—the company's branding so completely took over we forgot the product had a regular name.
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