Definition of "thermosetting" [thermosetting]

• Permanently hardening or solidifying on being heated. Used of certain synthetic resins. (adjective)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Includes discussion of natural polymers from tropical trees and the vulcanization of rubber, semi-synthetics (such as celluloid), thermosetting plastics (such as Bakelite), amino plastics (such as melamine), thermoplastics, and high-tech plastics."
• "Rifles were originally stocked with wood because the chemists of the late 1400s had not gotten around to inventing Kevlar, fiberglass, and thermosetting plastics."
• "Hexion says it's the world's largest producer of thermosetting resins, known in the trade as "thermosets.""