Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
dēsignātor or dissignātor (the latter form freq. in inscrr., and preferred by Brambach; so Keller, ad Hor. Ep. 1, 7, 5; Corp. Inscr. Lat. pp. 597, 768), ōris, m. [designo], one who regulates or arranges; a regulator.
As a t. t.,