Source : Webster's Revised Unabridged Dictionary (1913)

Malfeasance \Mal*fea"sance\, n. [F. malfaisance, fr. malfaisant
   injurious, doing ill; mal ill, evil + faisant doing, p. pr.
   of faire to do. See {Malice}, {Feasible}, and cf.
   {Maleficence}.] (Law)
   The doing of an act which a person ought not to do; evil
   conduct; an illegal deed. [Written also {malefeasance}.]

Source : WordNet®

malfeasance
     n : wrongful conduct by a public official