Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
2. incerto, āre, v. a. [incertus], to render doubtful or uncertain (ante- and postclass.): longa dies meum incertat animum, Plaut. Ep. 4, 1, 18: prospectum (cursus), App. M. 11, p. 265: singultu lacrimoso sermonem incertans, making indistinct, inaudible, id. ib. 5, p. 164: me incertat dictio, Pac. ap. Non. 123, 30 (Trag. Rel. p. 79 Rib.).