Curdled milk is a type of milk that has been thickened or soured by the addition of an acid or enzyme. CLABBER, which is seven letters long, is a type of curdled milk that is made by allowing raw milk to sit at room temperature until it thickens. Rennet, which is six letters long, is an enzyme that is used to curdle milk in cheese-making. Posset, also six letters long, is a type of curdled milk drink that is made with hot milk, sugar, and spices. Lastly, tofu, which is four letters long, is a type of curdled milk product that is made from soybeans.