The Collaborative International Dictionary of English v.0.48:

Exhortatory \Ex*hor"ta*to*ry\a. [L. exhortatorius: cf. F.
   exhortatoire.]
   Of or pertaining to exhortation; hortatory. --Holinshed.
   [1913 Webster]

WordNet (r) 3.0 (2006):

exhortatory
    adj 1: giving strong encouragement [syn: exhortative,
           exhortatory, hortative, hortatory]