1. When it coagulates, milk separates into a semisolid portion (curd) and a watery liquid (whey). cheese is made from the curd. 2. A creamy mixture made from juice (usually lemon, lime or orange), sugar, butter and egg yolks. The ingredients are cooked together until the mixture becomes quite thick. When cool, the lemon (or lime or orange) curd becomes thick enough to spread and is used as a topping for breads and other baked goods. Various flavors of curd are available commercially in gourmet markets and some supermarkets.