- A square, hollow place on the back of a calcining furnace, where tin ore is laid to dry.
- A large tub, such as is used for making wine or for tanning.
- (dated) A liquid measure and dry measure; especially, a liquid measure in Belgium and Holland, corresponding to the hectolitre of the metric system, which contains 22.01 imperial gallons, or 26.4 standard gallons in the United States. (The old Dutch grain vat averaged 0.762 Winchester bushel. The old London coal vat contained 9 bushels. The solid-measurement vat of Amsterdam contains 40 cubic feet; the wine vat, 241.57 imperial gallons, and the vat for olive oil, 225.45 imperial gallons.)
- (Roman Catholic) A vessel for holding holy water.
- (transitive) To blend (wines or spirits) in a vat; figuratively, to mix or blend elements as if with wines or spirits.