NOUN (2)

1. professional wrongdoing that results in injury or damage;
- Example: "the widow sued his surgeon for malpractice"

2. a wrongful act that the actor had no right to do; improper professional conduct;
- Example: "he charged them with electoral malpractices"

The Collaborative International Dictionary of English v.0.48:

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.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

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"

Moby Thesaurus II by Grady Ward, 1.0:

64 Moby Thesaurus words for "malpractice":
   abuse, abuse of office, bad policy, befoulment, conversion,
   corrupt administration, crime, criminal tendency, criminality,
   criminosis, debasement, defalcation, defilement, desecration,
   diversion, embezzlement, evil courses, evildoing, feloniousness,
   fouling, impolicy, inexpedience, inexpediency, lawbreaking,
   maladministration, malfeasance, malversation, misadministration,
   misapplication, misappropriation, misconduct, misdemeanor,
   misdirection, misdoing, misemployment, misfeasance, misgovernment,
   misguidance, mishandling, mismanagement, misprision,
   misprision of treason, misrule, misusage, misuse, neglect,
   negligence, nonfeasance, omission, peculation, perversion,
   pilfering, pollution, poor stewardship, positive misprision,
   profanation, prostitution, sin, thou scarlet sin, vice,
   viciousness, violation, wrong conduct, wrongdoing