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

Origin of keystone

First recorded in 1630–40; key1 + stone

Synonyms for keystone

See more synonyms for on Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for keystone

Contemporary Examples of keystone

Historical Examples of keystone

  • On this is the inscription: “Her loss was that as of a keystone to an arch.”

    Italy, the Magic Land

    Lilian Whiting

  • The keystone of the arch had been removed, the downfall of the whole must follow.

    Debts of Honor

    Maurus Jkai

  • In fact, not a few of us think that the Strathcona is the keystone of the Mission.

    A Labrador Doctor

    Wilfred Thomason Grenfell

  • That is the keystone of American liberty—'malice toward none.'

    Spring Street

    James H. Richardson

  • From the pavement to the keystone of its vault is but 132 French feet—about 150 English.

British Dictionary definitions for keystone


  1. Also called: headstone, quoin the central stone at the top of an arch or the top stone of a dome or vault
  2. 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