Definition of proline in English: noun ˈprəʊliːn ˈproʊˌlin. mass noun Biochemistry. An amino acid which is a constituent of most proteins, especially collagen. A heterocyclic compound; chemical formula: C₅H₉NO₂. Origin. Early 20th century: contraction of the chemical name p (yr)rol (id)ine-2-carboxylic acid. 顺带查了一下 ...