The Collaborative International Dictionary of English v.0.48:

Misdirection \Mis`di*rec"tion\, n.
   1. The act of directing wrongly, or the state of being so
      directed.
      [1913 Webster]

   2. (Law) An error of a judge in charging the jury on a matter
      of law. --Mozley & W.
      [1913 Webster]

   3. The direction of another's attention to an unimportant
      place or matter, for the purpose of being able to perform
      an action undetected; as, misdirection is an important
      part of a magician's art.
      [PJC]

WordNet (r) 3.0 (2006):

misdirection
    n 1: an incorrect charge to a jury given by a judge
    2: incorrect directions or instructions
    3: management that is careless or inefficient; "he accomplished
       little due to the mismanagement of his energies" [syn:
       mismanagement, misdirection]
    4: the act of distracting; drawing someone's attention away from
       something; "conjurers are experts at misdirection" [syn:
       distraction, misdirection]

Moby Thesaurus II by Grady Ward, 1.0:

42 Moby Thesaurus words for "misdirection":
   bad policy, bum steer, college of Laputa, corruption,
   false coloring, impolicy, inexpedience, inexpediency,
   maladministration, malfeasance, malpractice, misadministration,
   misconduct, misconstruction, misfeasance, misgovernment,
   misguidance, mishandling, misinformation, misinstruction,
   misinterpretation, misknowledge, misleading, mismanagement,
   misrepresentation, misrule, misteaching, misuse, mystification,
   neglect, negligence, nonfeasance, obfuscation, obscurantism,
   obscuration, omission, perversion, slanting, sophistry, straining,
   torturing, wrongdoing



Bouvier's Law Dictionary, Revised 6th Ed (1856):

MISDIRECTION, practice. An error made by a judge in charging the jury in a
special case.
     2. Such misdirection is either in relation to matters of law or matters
of fact.
     3.-1. When the judge at the trial misdirects the jury, on matters of
law, material to the issue, whatever may be the nature of the case, the
verdict will be set aside, and a new trial granted; 6 Mod. 242; 2 Salk. 649;
2 Wils. 269; or if such misdirection appear in the bill of exceptions or
otherwise upon the record, a judgment founded on a verdict thus obtained,
will be reversed. When the issue consists of a mixed question of law and
fact and there is a conceded state of facts, the rest is a question for the
court; 2 Wend. R. 596; and a misdirection in this respect will avoid the
verdict.
     4.-2. Misdirection as to matters of fact will in some cases be
sufficient to vitiate the proceedings. If, for example, the judge should
undertake to dictate to the jury. When the, judge delivers, his opinion to
the jury on a matter of fact, it should be delivered as mere opinion, and
not as direction. 12 John. R. 513. But the judge is in general allowed to
very liberal discretion in charging a jury on matters of fact. 1 McCl. & Y.
286.
     5. As to its effects, misdirection must be calculated to do injustice;
for if justice has been done, and a new trial would produce the same result,
a new trial will not be granted on that account, 2 Salk. 644, 646; 2 T. R.
4; 1 B. & P. 338; 5 Mass. R. 1; 7 Greenl. R. 442; 2 Pick. R. 310; 4 Day's R.
42; 5 Day's R. 329; 3 John. R. 528; 2 Penna. R. 325.