Source : Webster's Revised Unabridged Dictionary (1913)

Paralogism \Pa*ral"o*gism\, n. [Gr. ?, fr. ? to reason falsely;
   ? beside + ? to reason, ? discourse, reason: cf. F.
   paralogisme.] (Logic)
   A reasoning which is false in point of form, that is, which
   is contrary to logical rules or formul[ae]; a formal fallacy,
   or pseudo-syllogism, in which the conclusion does not follow
   from the premises.

Source : WordNet®

paralogism
     n : an unintentionally invalid argument