Plain English Meaning
A plastic that sets hard once it cures and stays that way. You cannot melt it down and reshape it later. In aircraft, it is the glue-like material that locks the fibers of a composite part together.
Full Definition
A type of plastic that, once cured by heat or a chemical reaction, hardens permanently into a rigid form and cannot be softened or reshaped by further heating. In aircraft composite construction, thermosetting plastics — most commonly epoxy, polyester, or vinyl ester resins — are used as the matrix that binds reinforcing fibers such as fiberglass, carbon, or aramid into a strong, lightweight structure.
Context Anchor
Seen in aircraft composite-material discussions, especially when describing the resins used to make composite aircraft parts.