Glass-reinforced plastic, but more commonly known as glass fibre (not fibreglass, which is a trade name). Used by most motorhome manufacturers, for everything from bumper surrounds to side skirts to complete bodyshells
Found on http://www.encyclo.co.uk/local/20699
GRP refers to the type of materials that the Laser II hull is made out of, it means that the hull is made out of combination of fibre glass and plastic. (GRP is short for Glass-Reinforced Plastic).
Found on http://www.jard.co.uk/laser2/glossary.shtml
Glass Reinforced Plastic, also known as fibreglass. GRP is a composite material made of a plastic reinforced by fine fibres of glass. GRP is an extremely tough material used in the marine industry for its hardwearing and weatherproof characteristics. GRP is also used as the outer skin on composite doors. Found on https://www.eurocell.co.uk/glossary