The Collaborative International Dictionary of English v.0.48:

Parisyllabic \Par`i*syl*lab"ic\, Parisyllabical
\Par`i*syl*lab"ic*al\, a. [Pari- + syllabic, -ical: cf. F.
   parisyllabique.]
   Having the same number of syllables in all its inflections.
   [1913 Webster]