Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
nūgālis, e, adj. [nugae], frivolous, trifling, worthless, empty (post-class.): theoremata, Gell. 1, 2, 6; Mart. Cap. 1, § 2 Kopp (al. nugalas): scholica quaedam, id. 4, 1, 1; 7, 17, 3: illa olim nugalia conscripsi, trifles, bagatelles, Front. de Fer. Als. 3 Mai.