Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
octōnārĭus, a, um, adj. [octoni], consisting of eight: numerus, Varr. L. L. 9, § 86 Müll.: versus, an Iambic verse of eight feet, Quint. 9, 4, 72; Diom. p. 514 P.: fistula, the plate for which was eight inches broad, Front. Aquaed. 28; 42; Plin. 31, 6, 31, § 58.