Fibreglass

Dictionary of Environmental Health

Properly a fibre made from molten glass that is then drawn out into very thin fibres.

The name is used in practice to include fibreglass matting reinforced with plastic material (glass fibrereinforced plastic or GRP) used as a construction or repair material and also (more incorrectly) to a range of plastic material used especially in DIY or repair applications for filling in holes or dents.