Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
pennŭla, ae, f. dim. [penna-potens], a little wing (rare but class.): cum pulli pennulis uti possunt, Cic. N. D. 2, 52, 129: tensa, Ven. Carm. 3, 22, 9; Hieron. adv. Pelag. 1, 14 init.; Vulg. Lev. 5, 8.