(Science: physiology) One of a class of amorphous nitrogenous principles, containing, as a rule, a small amount of sulphur; an albuminoid, as blood fibrin, casein of milk, etc. Proteids are present in nearly all animal fluids and make up the greater part of animal tissues and organs. They are also important constituents of vegetable tissues. See note under food. Proteid.
Origin: Gr. First.