Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
prō-nŭrus, ūs, f., a grandson’s wife, Dig. 38, 10, 4; Paul. ex Fest. p. 224 Müll.: pronurus et magni Laomedontis ero, i. e. the wife of Paris, who was grandson of Laomedon, Ov. H. 17, 206.