fiberglass

This term refers to a composite material that blends the tensile strength of glass fibers with the rigidity of a polymer resin. It is characterized by its high strength-to-weight ratio and resistance to corrosion, making it a staple in marine and automotive engineering. In a residential context, the word often refers specifically to the fluffy, mineral-wool style insulation used in walls and attics. Because it is an uncountable mass noun, it does not take a plural form when referring to the material itself; instead, quantities are measured using terms like "sheets of" or "rolls of" fiberglass.