'Coign' definitions:

Definition of 'coign'

noun

Expandable metal or wooden wedge used by printers to lock up a form within a chase [syn: quoin, coign, coigne]

noun

The keystone of an arch [syn: quoin, coign, coigne]

From: GCIDE

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]