noun
: a firm relatively inextensible rubber or rubber product: as
a. : a normally black substance having the texture of horn and made by vulcanizing natural rubber with high percentages (as about 30 to 50 percent) of sulfur and with or without other compounding ingredients
b. : a similar substance made from certain synthetic rubbers (as GR-S and nitrile rubber) and sulfur
c. : a similar substance made from natural or certain synthetic rubbers by the use of organic vulcanizing agents without elemental sulfur