The Collaborative International Dictionary of English v.0.48:

Irrision \Ir*ri"sion\, n. [L. irrisio, fr. irridere, irrisum, to
   laugh at; pref. ir- in + ridere to laugh: cf. F. irrision.]
   The act of laughing at another; derision.
   [1913 Webster]

         This being spoken sceptic[`e], or by way of irrision.
                                                  --Chapman.
   [1913 Webster]