1. Loss of the power to perform rapid alternating movements: This symptom of adiadochocinesia is indicative of a disorder of the cerebellum or its tracts.

Adiadochokinesis involves the inability to stop one movement and then to follow it immediately with another motion in the opposite direction.

2. The inability to perform rapid alternating movements of one or more of the body's extremities: Adiadochocinesis is sometimes requested by physicians during physical examinations so they can determine if the patient has any neurological problems.
3. Etymology: a highly contrived word that is composed of the Greek a-, "without" + diadochos, "successive" + kinesis, "motion".

So, adiadochokinesis is a neurological sign of the inability to perform rapid alternating movements; such as, pronation (turning the hand so the palm faces downward or backward) and supination (having the palm of the hand facing upward).