Turn (the hand or forearm) so that the back is downward or backward, or turn out (the leg) WordNet 3.0 & Open English WordNet

To twist the forearm so as to turn the palm of the hand backwards if the forearm is pointing up, upwards if the forearm is horizontal, or forwards if the arm is pointing down; to twist the forearm by contracting the biceps brachii; to twist the right forearm clockwise or the left forearm counterclockwise. Wiktionary