the performance by a public official of an act that is legally unjustified, harmful, or contrary to law; wrongdoing (used especially of an act in violation of a public trust). Compare misfeasance( def 2 ), nonfeasance.
1690s, from Fr. malfaisance "wrongdoing," from mal- "badly" (see mal-) + faisant, prp. of faire "to do," from L. facere "to do" (see factitious). Malfeasor "wrong-doer" is attested from early 14c. Related: Malfeasant.