The Collaborative International Dictionary of English v.0.48:

Mismanage \Mis*man"age\, v. t. & i.
   To manage ill or improperly; as, to mismanage public affairs.
   [1913 Webster]

WordNet (r) 3.0 (2006):

mismanage
    v 1: manage badly or incompetently; "The funds were mismanaged"
         [syn: mismanage, mishandle, misconduct]

Moby Thesaurus II by Grady Ward, 1.0:

42 Moby Thesaurus words for "mismanage":
   abuse, be negligent, befoul, convert, debase, defalcate, defile,
   desecrate, divert, do amiss, embezzle, foul, maladminister,
   misadminister, misapply, misappropriate, miscall, miscite,
   misconduct, miscount, misdeal, misdirect, misemploy, misfield,
   misgovern, misguide, mishandle, misplay, misprint, misquote,
   misread, misreport, misrule, misspell, misuse, peculate, pervert,
   pilfer, pollute, profane, prostitute, violate