A lack of or a lapse of posture consisting of momentary loss of a fixed position of the hands or arms followed by a jerking recovery movement that restores the limb to its original position; also known as "flapping tremor": Abnormal muscle tremor consisting of involuntary jerking of the hands is known as asterixis and it involves a shaking of the wrists and hands when the arms are extended and they are described as resembling a bird flapping its wings.