Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
cantērīnus (canth-), a, um, adj. [canterius], of or pertaining to a horse, horse-: ritus, like a horse, Plaut. Men. 2, 3, 44: hordeum, i. e. winter barley, Col. 2, 9, 14; 2, 10, 31; Pall. Oct. 1, 2: lapathum = rumex, Plin. 20, 21, 85, § 231.