The Collaborative International Dictionary of English v.0.48:

Misfeasance \Mis*fea"sance\, n. [OF. pref. mes- wrong (L. minus
   less) + faisance doing, fr. faire to do, L. facere. Cf.
   Malfeasance.] (Law)
   A trespass; a wrong arising from an overt act; the improper
   doing of an act which a person might lawfully do. --Bouvier.
   --Wharton.
   [1913 Webster]

WordNet (r) 3.0 (2006):

misfeasance
    n 1: doing a proper act in a wrongful or injurious manner