Definition: Mac20 refers to a two-inch round metal plate commonly used in making bread rolls, buns, and other baked goods for use as an ingredient or a decoration on top of them. It's often found alongside dough or in baker's marks. The word "mac" comes from the Latin term 'mace', which means "little stone". So, "Mac20" stands for a small piece of bread-like material used in baking to decorate other ingredients like rolls and buns.