Contra or Contrary Body Movement Position is often used in steps that require you to be out of line with your partner. In the technique books, it is defined as: "A foot position where the foot is placed on or across the line of the supporting foot, either in front or behind, to maintain body line".
Essentially, this means that you are keeping your upper body facing one direction while your lower body faces a different one. This is generally accomplished by leaving the shoulders where they were in the previous step and allowing the legs to take a new direction.
However! You should not lose connection with your partner when in CBMP and should work even harder to keep your centres facing each other.