[1] : The Collaborative International Dictionary of English v.0.48

coign \coign\ koin, n.
   a var. spelling of coin, quoin, a corner, wedge; --
   chiefly used in the phrase coign of vantage, a position
   advantageous for action or observation.
   webster 1913 suppl.

         from some shielded nook or coign of vantage. --the
                                                  century.
   webster 1913 suppl.

         the lithosphere would be depressed on four faces; . . .
         the four projecting coigns would stand up as
         continents.                              --nature.
   webster 1913 suppl.

   2. an expandable metal or wooden wedge used by printers to
      lock up a form within a chase.

   syn: quoin, coigne.
        wordnet 1.5

   3. the keystone of an arch.

   syn: quoin, coigne.
        wordnet 1.5
see also:
coin quoin 

[2] : WordNet (r) 2.0

coign
     n 1: expandable metal or wooden wedge used by printers to lock up
          a form within a chase syn: quoin, coigne
     2: the keystone of an arch syn: quoin, coigne
see also:
quoin coigne 

Coign >> C Words
Coign, definition of term: Coign
coign_pag1.html