Source : Webster's Revised Unabridged Dictionary (1913)

Imparisyllabic \Im*par"i*syl*lab"ic\, a. [L. impar unequal + E.
   syllabic: cf. F. imparisyllabique.] (Gram.)
   Not consisting of an equal number of syllables; as, an
   imparisyllabic noun, one which has not the same number of
   syllables in all the cases; as, lapis, lapidis; mens, mentis.