The Collaborative International Dictionary of English v.0.48:

contraclockwise \contraclockwise\ adj.
   in the direction opposite to the rotation of the hands of a
   clock; counterclockwise. Opposite of clockwise. [Also See:
   sinistral.]

   Syn: counterclockwise, anticlockwise.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

contraclockwise
    adj 1: in the direction opposite to the rotation of the hands of
           a clock [syn: counterclockwise, anticlockwise,
           contraclockwise] [ant: clockwise]