Source : Webster's Revised Unabridged Dictionary (1913)

Malpractice \Mal*prac"tice\, n. [Mal- + practice.]
   Evil practice; illegal or immoral conduct; practice contrary
   to established rules; specifically, the treatment of a case
   by a surgeon or physician in a manner which is contrary to
   accepted rules and productive of unfavorable results.
   [Written also {malepractice}.]

Source : WordNet®

malpractice
     n 1: professional wrongdoing that results in injury or damage;
          "the widow sued his surgeon for malpractice"
     2: a wrongful act that the actor had no right to do; improper
        professional conduct; "he charged them with electoral
        malpractices"