The Collaborative International Dictionary of English v.0.48:

Misdeed \Mis*deed"\, n. [AS. misd[=ae]d. See Deed, n.]
   An evil deed; a wicked action.
   [1913 Webster]

         Evils which our own misdeeds have wrought. --Milton.
   [1913 Webster]

   Syn: Misconduct; misdemeanor; fault; offense; trespass;
        transgression; crime.
        [1913 Webster]

WordNet (r) 3.0 (2006):

misdeed
    n 1: improper or wicked or immoral behavior [syn: misbehavior,
         misbehaviour, misdeed]

Moby Thesaurus II by Grady Ward, 1.0:

52 Moby Thesaurus words for "misdeed":
   atrocity, breach, crime, crime against humanity, deadly sin,
   delinquency, dereliction, enormity, error, evil, failure, fault,
   felony, genocide, guilty act, heavy sin, impropriety, indiscretion,
   inexpiable sin, iniquity, injury, injustice, lapse, malefaction,
   malfeasance, malum, minor wrong, misconduct, misdeeds, misdemeanor,
   misdoing, misfeasance, mortal sin, nonfeasance, offense, omission,
   outrage, peccadillo, peccancy, sin, sin of commission,
   sin of omission, sinful act, slip, tort, transgression, trespass,
   trip, unutterable sin, venial sin, wrong, wrongdoing