Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
cŏhorto, āre, 1, v. a. (rare collat. form of cohortor), to exhort, encourage: et dicerent castra capta esse, atque hos cohortarent uti maturarent, Quadrig. ap. Non. p. 472, 19: exercitus pransus, paratus, cohortatus, Cat. ap. Gell. 15, 13, 5; v. cohortor.