[pro.tein] n, often attrib [F proteine, fr. LGk proteios primary, fr. Gk protos first--more at prot-] (ca. 1844) 1: any of numerous naturally occurring extremely complex substances that consist of amino-acid residues joined by peptide bonds, contain the elements carbon, hydrogen, nitrogen, oxygen, usu. sulfur, and occas. other elements (as phosphorus or iron), and include many essential biological compounds (as enzymes, hormones, or immunoglobulins)
2: the total nitrogenous material in plant or animal substances