Source : Webster's Revised Unabridged Dictionary (1913)

Sophistic \So*phis"tic\, Sophistical \So*phis"tic*al\, a. [L.
   sophisticus, Gr. ?: cf. F. sophistique.]
   Of or pertaining to a sophist; embodying sophistry;
   fallaciously subtile; not sound.

         His argument . . . is altogether sophistical.
                                                  --Macaulay.
   -- {So*phis"tic*al*ly}, adv. -- {So*phis"tic*al*ness}, n.

Source : WordNet®

sophistical
     adj : plausible but misleading [syn: {sophistic}]