n. 1 a hard deposit of saliva, calcium phosphate, etc., that forms on the teeth. 2 a deposit of acid potassium tartrate that forms a hard crust on the inside of a cask during the fermentation of wine. tartar emetic potassium antimony tartrate used as a mordant and in medicine (formerly as an emetic). tartarize v.tr. (also -ise).
[ ME f. med.L f. med.Gk tartaron ]