Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
disserto, āvi, ātum, 1, v. freq. a. [dissero], to discuss, argue, debate a thing; or to dispute, converse, treat respecting a thing (ante-class. and post-Aug., esp. in Tac.): quid ego cum illo dissertem amplius? Cato ap. Paul. ex Fest. p. 60, 1 Müll.: dic mihi istuc, quod vos dissertatis, Plaut. Men. 5, 2, 58; cf.: vim Romanam pacisque bona dissertans, Tac. H. 4, 69; so, haec atque talia, id. A. 12, 11.
Absol.: ostentandi gratia magno conventu hominum, Gell. 7, 14, 9: totis exercitibus coram dissertare, Tac. A. 13, 38.