Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
rŭbellus, a, um, adj. dim. [ruber], reddish: Veientanum (vinum), Mart. 1, 104, 9, Pers. 5, 147; cf. vineae, Plin. 14, 2, 4, § 23: calvitium, Mart. Cap. 8, § 804.