Ord·nance n. Heavy weapons of warfare; cannon, or great guns, mortars, and howitzers; artillery; sometimes, a general term for all weapons, ammunitiion, and appliances used in war.
All the battlements their ordnance fire. --Shak.
Then you may hear afar off the awful roar of his [Rufus Choate's] rifled ordnance. --E. Everett.
Ordnance survey, the official survey of Great Britain and Ireland, conducted by the ordnance department.
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Ordnance Survey
n : the official cartography agency of the British government