The Collaborative International Dictionary of English v.0.48:

Misinform \Mis`in*form"\, v. t.
   To give untrue information to; to inform wrongly.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Misinform \Mis`in*form"\, v. i.
   To give untrue information; (with against) to calumniate.
   [R.] --Bp. Montagu.
   [1913 Webster]

WordNet (r) 3.0 (2006):

misinform
    v 1: give false or misleading information to [syn: misinform,
         mislead]