Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Perseus.
Tēĭus, a, um, v. Teos.
Tĕos or Tĕus, i, f., = Τέως, a town in Ionia, the birthplace of the poet Anacreon, Mel. 1, 17, 3; Liv. 37, 27, 9.
Hence, Tēĭus, a, um, adj., of or belonging to Teos, Teian: Anacreon, Hor. Epod. 14, 10; cf. Musa, Ov. Tr. 2, 364; id. A. A. 3, 330; id. R. Am. 762: fides, Hor. C. 1, 17, 18.
Plur.: Tēĭi, ōrum, m., the inhabitants of Teos, Teians, Liv. 37, 12 and 28.