Definitions for Keystoneˈkiˌstoʊn
Random House Webster's College Dictionary
the wedge-shaped piece at the summit of an arch, regarded as holding the other pieces in place.
Category: Building Trades
something on which associated things depend; foundation.
anchor, mainstay, keystone, backbone, linchpin, lynchpin(noun)
a central cohesive source of support and stability
"faith is his anchor"; "the keystone of campaign reform was the ban on soft money"; "he is the linchpin of this firm"
keystone, key, headstone(noun)
the central building block at the top of an arch or vault
The top stone of an arch.
A native or resident of the American state of Pennsylvania.
the central or topmost stone of an arch. This in some styles is made different in size from the other voussoirs, or projects, or is decorated with carving. See Illust. of Arch