Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
per-lĕvis, e, adj., very light, very slight: momentum, Cic. Agr. 2, 29, 80; Liv. 21, 43, 11; 24, 34, 2.
Adv.: per-lĕvĭter, very lightly, very slightly: commotus, Cic. Q. Fr. 2, 6, 1; id. Tusc. 3, 25, 61.