Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
pĕtesso and pĕtisso, ĕre, v. intens. a. [peto], to strive after or seek for repeatedly or eagerly, to pursue; with acc. (rare but class.): petissere antiqui pro petere dicebant. Sed, ut mihi videtur, cum significabant saepius petere, Fest. p. 206 Müll.; cf.: petissere petere, Paul. ex Fest. p. 212 ib.: pugnam caedesque petessit, Lucr. 3, 648: auras petessens, id. 5, 810: laudem, Cic. Tusc. 2, 26, 62.