n. 1 mounted guns; cannon. 2 a branch of government service dealing esp. with military stores and materials. ordnance datum Brit. mean sea level as defined for Ordnance Survey. Ordnance map Brit. a map produced by Ordnance Survey. Ordnance Survey Brit. (in the UK) an official survey organization, orig. under the Master of the Ordnance, preparing large-scale detailed maps of the whole country.
[ ME var. of ORDINANCE ]