Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
orbītus, a, um [orbis], circular (anteand post-class.): motu, Varr. ap. Non. 148, 16; Arn. 2, 83 (others read orbico; cf. Oehler ad Varr. Sat. Menipp. p. 139).