The Collaborative International Dictionary of English v.0.48:

Freakish \Freak"ish\, a.
   Apt to change the mind suddenly; whimsical; capricious.
   [1913 Webster]

         It may be a question whether the wife or the woman was
         the more freakish of the two.            --L'Estrange.
   [1913 Webster]

         Freakish when well, and fretful when she's sick.
                                                  --Pope.

   2. rapidly changing and unpredictable; as, freakish weather.
      [PJC]

   3. markedly abnormal.

   Syn: freaky.
        [PJC] -- Freak"ish*ly, adv. -- Freak"ish*ness, n.
        [1913 Webster]

WordNet (r) 3.0 (2006):

freakishly
    adv 1: unpredictably; "the weather has been freakishly variable"
           [syn: capriciously, freakishly]