Longman Dictionary English From Longman Dictionary of Contemporary EnglishRelated topics: Plasticsthermosettingther‧mo‧set‧ting /ˈθɜːməʊˌsetɪŋ $ ˈθɜːrmoʊ-/ adjective technical HCPthermosetting plastic becomes hard and unbendable after it has been heated ldoceonline.com