What does fibreglass mean?
Fibreglass is a versatile man-made material formed by drawing molten glass into extremely fine filaments. Woven into cloth or pressed into mats and bonded with polyester or epoxy resin, these fibres produce a composite that is strong, rigid and remarkably light, which is why it dominates applications ranging from small-boat hulls and car bodies to water tanks, surfboards and roofing panels. In its unbonded form, as fluffy glass wool, fibreglass is also one of the most widely used thermal insulators in buildings. The noun is uncountable and most often appears attributively, as in 'fibreglass boat' or 'fibreglass roof'. It carries neutral, practical connotations, evoking DIY repairs, industry and mid-century modern furniture design. The American spelling is fiberglass, and both forms refer to precisely the same material.
nounA lightweight but strong material consisting of fine filaments of glass woven or matted together, often combined with resin to form a mouldable composite used in boat hulls, car bodies and insulation.
- A composite material made of fine glass filaments, typically bonded with resin, used for lightweight moulded structures.
- (uncountable, attributive) Glass wool used chiefly as thermal insulation.
"The dinghy's hull was made entirely of fibreglass, making it light enough for one person to carry."
"The repair kit included resin and a sheet of fibreglass matting."
"Loft insulation is usually a thick blanket of fibreglass laid between the joists."
Fibreglass has no standard plural because it denotes a substance rather than countable items; quantity is expressed with terms like 'sheets of fibreglass' or 'layers of fibreglass'.
"He cut two sheets of fibreglass to fit the panel."
It's made from the same stuff as windows, yet spun into threads finer than human hair, fibreglass can be moulded into boats, cars and even aircraft parts.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of fibreglass
The word combines 'fibre', borrowed from Old French 'fibre' and ultimately from Latin 'fibra', meaning a filament or thread, with 'glass', from Old English 'glæs'. The material itself was developed in the 1930s when techniques for mass-producing fine glass fibres were perfected, and compounds like 'fibreglass' arose shortly afterwards to name the resulting products. The Latin root 'fibra' also gives English words such as 'fibrous' and 'fibril'.
How fibreglass is actually used
Uncountable in normal use, so it takes singular verbs and no plural in ordinary contexts. The word functions attributively far more often than predicatively, appearing mainly before nouns naming manufactured objects.
Easily confused with fibreglass
'Fibreglass' is simply the British spelling while 'fiberglass' is the American spelling of exactly the same material.