From Longman Dictionary of Contemporary EnglishOrdnance Survey mapˌOrdnance ˈSurvey ˌmap noun [countable] British English SGa map which shows all the roads, paths, hills etc of an area in detail
Examples from the Corpus
Ordnance Survey map• Lorton paused to consult his Ordnance Survey map.• Filling a substantial amount of skyline and covering six full squares of the Ordnance Survey map.Origin Ordnance Survey map (1800-1900) Because the maps were originally made for the department responsible for ordnance: ordnance “military materials” ((14-20 centuries)), from Old French ordenance 