Source : Webster's Revised Unabridged Dictionary (1913)

Unbalanced \Un*bal"anced\, a. [In senses 1 and 2, pref. un- not
   + balanced; in sense 3, 1st pref. un- + balance.]
   1. Not balanced; not in equipoise; having no counterpoise, or
      having insufficient counterpoise.

            Let Earth unbalanced from her orbit fly. --Pope.

   2. (Com.) Not adjusted; not settled; not brought to an
      equality of debt and credit; as, an unbalanced account;
      unbalanced books.

   3. Being, or being thrown, out of equilibrium; hence,
      disordered or deranged in sense; unsteady; unsound; as, an
      unbalanced mind. --Pope.

Source : WordNet®

unbalanced
     adj 1: being or thrown out of equilibrium [syn: {imbalanced}] [ant:
             {balanced}]
     2: affected with madness or insanity; "a man who had gone mad"
        [syn: {brainsick}, {crazy}, {demented}, {distracted}, {disturbed},
         {mad}, {sick}, {unhinged}]
     3: debits and credits are not equal