an alcoholic liquor, or mixture of alcohol and water, containing a standard amount of alcohol. In the U.S. proof spirit has a specific gravity of .93353 (containing one half of its volume of alcohol of a specific gravity of .7939 at 60° F). In Britain proof spirit has a specific gravity of .91984.
(in Britain and Canada) a mixture of alcohol and water or an alcoholic beverage that contains 49.28 per cent of alcohol by weight, 57.1 per cent by volume at 51°F: up until 1980 used as a standard of alcoholic liquids
(in the US) a similar standard mixture containing 50 per cent of alcohol by volume at 60°F