- soft and pliable when heated, as some plastics, without any change of the inherent properties.
- a plastic of this type.
- (of a material, esp a synthetic plastic or resin) becoming soft when heated and rehardening on cooling without appreciable change of propertiesCompare thermosetting
- a synthetic plastic or resin, such as polystyrene, with these properties
adj.1883, see thermo- + plastic. As a noun from 1929.
- Of or relating to a compound that can be repeatedly made soft and hard through heating and cooling. Polyethylene and polystyrene are thermoplastic resins. Compare thermosetting.