- the central, topmost voussoir of an arch, popularly thought of as especially holding the others in place
- that one of a number of associated parts or things that supports or holds together the others; main part or principle
designating, of, or like the slapstick comedy of a series of silent films featuring a bungling, inept squad of policemen (Keystone Kops or Keystone Cops) in wild chases, etc.
Origin of Keystoneafter Keystone Comedy Co., the film producers
- Architecture The central wedge-shaped stone of an arch that locks its parts together. Also called headstone.
- The central supporting element of a whole.