THERMOPLASTIC
thermoplastic
(adjective) having the property of softening or fusing when heated and of hardening and becoming rigid again when cooled; “thermoplastic materials can be remelted and cooled time after time without undergoing any appreciable chemical change”
thermoplastic, thermoplastic resin
(noun) a material that softens when heated and hardens again when cooled
Source: WordNet® 3.1
Etymology
Adjective
thermoplastic (not comparable)
softening when heated and hardening when cooled, and thus able to be moulded
Coordinate terms
• thermosetting
Noun
thermoplastic (usually uncountable, plural thermoplastics)
A plastic with this property.
Source: Wiktionary