Keystone

Webster's Dictionary of the English Language

·noun 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.

Related Words

Keystone State
·add. ·- Pennsylvania; — a nickname alluding to its having been the central one of the 13 original ...

Webster's Dictionary of the English Language
keystone state
The State of Pennsylvania. So called from its being the central State of the Union at the time of th...

Dictionary of American Words And Phrases by John Russell Bartlett.