Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† pentămĕter, tri, m., = πεντάμετρος (containing five metrical feet), a pentameter: in pentametri medio, Quint. 9, 4, 98; so id. 9, 4, 109: heroicus, Diom. p. 506 P.: pentametrum elegum, id. p. 502 ib.