To vulcanize is to submit rubber to a process that makes it hard. Charles Goodyear, whose name is synonymous with car tires, first developed the method used to vulcanize rubber.
If it weren't for the ability to vulcanize rubber, a process that involves using chemicals to strengthen it, our lives would look very different than they do. We use this hardened rubber in objects including the tires on our cars, rubber hoses, the soles of our shoes, and those red rubber balls we use to play kickball. Before it came to describe this process, vulcanize meant "put into flames," from the Roman god of fire, Vulcan.