Backswing interference is defined as:

• A. The batter contacts the catcher or his equipment after the time of the pitch.
• B. The batter contacts the catcher or his equipment prior to the time of the pitch.
• C. The batter's swing goes all the way around and his bat hits the catcher on his back.
• D. None of the above.

Answer: (B)

Backswing interference happens when the batter’s backswing contacts the catcher or the catcher’s equipment before the pitch is delivered. This pre-pitch contact interferes with the catcher’s opportunity to receive the pitch, so it’s considered interference for that moment in time. The other scenarios describe contact after the pitch has started or misrepresent the swing, which isn’t how this rule is defined. So the pre-pitch backswing contact with the catcher is the correct definition.