bouncing putty: a soft elastic silicone polymer that increases in elasticity with the application of force; used in the center of golf balls and as shock-absorbent padding
silicone: any of a large class of siloxanes that are unusually stable over a wide range of temperatures; used in lubricants and adhesives and coatings and synthetic rubber and electrical insulation
ballast: any heavy material used to stabilize a ship or airship