Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
1. rĕsŏnus, a, um, adj. [resono], resounding, re-echoing (poet.): voces, Ov. M. 3, 496: valles, Luc. 7, 480: ictus, Val. Fl. 1, 618: ripae, Sil. 6, 285: resonas plaudere caetras, id. 3, 348.