Definitions:

1. A lack or ordinary skill, negligence, misconduct, or a breach of duty in the performance of a professional service. NOUN
   • The engineer's malpractice in designing the bridge resulted in its structural failure.
2. Failure to act correctly or legally when doing your job, often causing injury or loss. NOUN
   • Many historians argue that colonial powers engaged in malpractice when exploiting resources and suppressing local cultures.
3. Improper, illegal, or negligent professional activity or treatment, especially by a medical practitioner, lawyer, or public official. NOUN
   • The deceased patient's spouse sued their surgeon for malpractice.

Synonyms:

• breach of duty
• dereliction of duty
• incompetence
• inefficiency
• irresponsibility
• misconduct
• mismanagement
• negligence
• professional negligence
• unprofessionalism