A tall, wide pot fitted with a rack that holds filled jars off the base, deep enough that boiling water covers the jar lids by an inch or two. It is the vessel for water-bath canning: high-acid foods such as jam, fruit, tomatoes with added acid and pickles are sealed in mason jars, held in the boiling water for the time the recipe sets, and vacuum-seal as they cool. Also called a water-bath canner.
The rack keeps jars from rattling against the bottom and cracking, and lifts them all out together. Low-acid foods such as plain vegetables, meat and stock cannot be made safe in boiling water and need a pressure canner instead; a water-bath pot does not reach the temperature that kills botulism spores.