Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
in-sībĭlo, 1, v. n. and a., to hiss, whistle, or rustle in (poet.): Eurus, Ov. M. 15, 603: ignis membris, Sil. 12, 616: Erinys atros insibilat ore tumores, hisses in, breathes in, with a hissing noise, id. 2, 626.