Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
sesquĭ-alter, ĕra, ĕrum, adj., once and a half (ἐπιδεύτερος), Cic. Univ. 7, 20 sqq.; Vitr. 3, 1 med.; App. Mag. p. 330 med.