Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
hĕbĕtesco, ĕre, v. inch. n. [hebes], to grow dull, dim, or faint (post-Aug. and very rare): aciem in cultris tonsorum, Plin. 28, 7, 23, § 79: acies oculi hebetescit ac paene caligat, Cels. 6, 6, 37: dolor hebetescit, Scrib. Comp. 56.