VERB (3)

1. pedal backwards on a bicycle;

2. step backwards, in boxing;

3. modify one's opinion, make it less strong;

The Collaborative International Dictionary of English v.0.48:

backpedal \back"ped*al\ v. i.
   1. pedal backwards, as on a bicycle.
      [WordNet 1.5]

   2. step backwards, in boxing.
      [WordNet 1.5]

   3. modify one' opinion, usually by making it less strong or
      adding qualifications.
      [WordNet 1.5] Backpiece

WordNet (r) 3.0 (2006):

backpedal
    v 1: pedal backwards on a bicycle
    2: step backwards, in boxing
    3: modify one's opinion, make it less strong