According to the captain and the first officer, they were instructed to taxi the airplane to an unspecified deice area to remove frost from the airframe. As they taxied, a ground crewmember stood by the wing to ensure the airplane?s clearance from another airline?s equipment and signaled thumbs up to the flight crew to indicate when they were clear of the equipment. After taxiing a short distance, the flight crew stopped and awaited further instructions from a ramp agent on the radio for positioning the airplane. Unknown to the flight crew, the deicing team misunderstood the thumbs-up signal to mean that deicing could begin. Consequently, they moved into a position behind the airplane?s left wing and in front of the left horizontal tail. The ramp agent working the radio could not see the airplane from the radio location and, believing it was still at the gate, instructed the flight crew to taxi 50 feet and stop for deicing. The flight crew initiated taxiing and almost immediately felt a bump, colliding with the boom arm of the deice truck. They then stopped the airplane. The deice truck was not equipped for radio communication; therefore, the team?s movement and position could not be coordinated with the other ground personnel or flight crew. Probable Cause: The inadequate communication among ground crew personnel, which resulted in the airplane?s collision with a deice truck.