Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† arctōus, a, um, adj., = ἀρκτῷος, prop., pertaining to arctos (q. v.); hence, poet., northern (syn.: arcticus, aquilonius, Borealis), Mart. 5, 68; 10, 6, 2; Luc. 1, 53; 10, 250; Sen. Oedip. 604; id. Herc. Oet. 1566.