Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
immurmŭro (inm-), āre, v. n. [inmurmuro], to murmur in, at, or against any thing (poet. and in post-class. prose): ipsa jacet terraeque tremens immurmurat atrae, Ov. M. 6, 558: terrae, id. ib. 11, 187: undis, id. ib. 11, 567: silvis Auster, Verg. G. 4, 261: hastae, Sil. 5, 332: tacita aure (Acestae), Stat. Th. 1, 532: undis, id. ib. 11, 567: illa sibi introrsum et sub lingua immurmurat, Pers. 2, 9: increpor a cunctis totumque immurmurat agmen, Ov. M. 3, 646: ipse publicato nobis, quod immurmurat, whispers, Macr. S. 6, 7: cum saepe immurmurantes audierit ventos, Amm. 12, 16.