Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ob-brūtesco, tŭi, 3, v. inch. n., to become brutish, stupid (ante- and post-class.): obbrutuit, obstupuit, a bruto, quod antiqui pro gravi, interdum pro stupido dixerunt. Afranius: non possum verbum facere, obbrutui, Paul. ex Fest. p. 187 Müll.: anima contracta suis e partibus obbrutescat, Lucr. 3, 545 (also ap. Non. 77, 32): claude meatus Obbrutescentis capitis, Prud. Hamart. 652.