The Collaborative International Dictionary of English v.0.48:

Mistrust \Mis*trust"\, n.
   Want of confidence or trust; suspicion; distrust. --Milton.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Mistrust \Mis*trust"\, v. t.
   1. To regard with jealousy or suspicion; to suspect; to doubt
      the integrity of; to distrust.
      [1913 Webster]

            I will never mistrust my wife again.  --Shak.
      [1913 Webster]

   2. To forebode as near, or likely to occur; to surmise.
      [1913 Webster]

            By a divine instinct, men's minds mistrust
            Ensuing dangers.                      --Shak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

mistrust
    n 1: doubt about someone's honesty [syn: misgiving,
         mistrust, distrust, suspicion]
    2: the trait of not trusting others [syn: distrust,
       distrustfulness, mistrust] [ant: trust, trustfulness,
       trustingness]
    v 1: regard as untrustworthy; regard with suspicion; have no
         faith or confidence in [syn: distrust, mistrust,
         suspect] [ant: bank, rely, swear, trust]

Moby Thesaurus II by Grady Ward, 1.0:

55 Moby Thesaurus words for "mistrust":
   Pyrrhonism, apprehension, apprehensiveness, awake a doubt,
   be diffident, be doubtful, be dubious, be possessive, be skeptical,
   be uncertain, beware, cageyness, call in question, challenge,
   chariness, contest, diffidence, dispute, distrust, distrustfulness,
   doubt, doubtfulness, dubiety, dubiousness, greet with skepticism,
   half believe, half-belief, harbor suspicions, have reservations,
   leeriness, misdoubt, misgive, misgiving, mistrustfulness, query,
   question, raise a question, reservation, scepticism, scruple,
   scrupulousness, self-doubt, shadow of doubt, skepticalness,
   skepticism, smell a rat, suspect, suspicion, suspiciousness,
   throw doubt upon, total skepticism, treat with reserve,
   uncertainty, unsureness, wariness