[ kee-stohn ]
/ ˈkiˌstoʊn /


the wedge-shaped piece at the summit of an arch, regarded as holding the other pieces in place.
something on which associated things depend: the keystone of one's philosophy.
Also called keystone sack. Baseball Slang. second base(def 1).

Nearby words

  1. keyring drive,
  2. keys,
  3. keyserling,
  4. keyslot,
  5. keysmash,
  6. keystone comedy,
  7. keystone joist,
  8. keystone kop,
  9. keystone species,
  10. keystone state

Origin of keystone

First recorded in 1630–40; key1 + stone Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for keystone

British Dictionary definitions for keystone


/ (ˈkiːˌstəʊn) /


Also called: headstone, quoin the central stone at the top of an arch or the top stone of a dome or vault
something that is necessary to connect or support a number of other related things
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for keystone



"stone in the middle of an arch, which holds up the others," 1630s, from key (n.1) in figurative sense of "that which holds together other parts" + stone. Figurative sense is from 1640s. Pennsylvania was called the Keystone State because of its position (geographical and political) in the original American confederation, between northern states and southern ones. Keystone cops were the bumbling police in the slapstick silent movies produced by Keystone Company, formed by Canadian-born U.S. film director Mack Sennett (1884-1960) in 1912.

Online Etymology Dictionary, © 2010 Douglas Harper