ordnance, ordenance, ordinance, or do nance

[The same word as ordinance (q.v.).] The original meaning was the bore or size of the gun, and thence the word came to be applied to the gun itself, exactly as in the case of Caliver (Skeat).] [ORDINANCE.) Cannons, mortars, great guns, howitzers; firearms too large and heavy to be fired from the person; frequently applied to all sorts of artillery. ordnance datum, s. Surv.: A fixed level to which all the levels taken in the British ordnance survey are referred. It is a point or level twelve feet six inches below Trinity High-water mark, or four feet six inches above Trinity Low-water mark. ordnance-survey, subst . The official survey of Great Britain and Ireland, carried out at the expense of the country by the Royal Engineers, a isted by civilians.