Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† bĭson, ontis, m., = βίσων [acc. to Oppian. Cyn. 2, 155, named from the Thracian Βίστονες], a species of wild ox living in northern regions, the Urus, the humpbacked ox, bison: Bos bison, Linn.; Plin. 8, 15, 15, § 38; Sen. Hippol. 65; Mart. Spect. 23, 4; Sol. 20.