My Food Glossary protein noun Any of a class of nitrogenous organic compounds that have large molecules composed of one or more long chains of amino acids and are an essential part of all living organisms, especially as structural components of body tissues such as muscle, hair, etc., and as enzymes and antibodies. Example: Animal protein is an important part of the human diet. fr: protéine Your browser does not support the audio element. This glossary was made with the Virtual Writing Tutor glossary maker and grammar checker .