tartar

sauce n. Sauce of mayonnaise and chopped gherkins, capers, etc. [from *tartar]

n. A reddish crust or sediment in wine casks, consisting essentially of crude cream of tartar, and used in marking pure cream of tartar, tartaric acid, potassium carbonate, black flux, etc., and, in dyeing, as a mordant for woolen goods; -- called also argol, wine stone, etc.