Akinesia refers to a Motor disturbance in which a person's muscles become rigid and movement is difficult to initiate.
Other /More definition:
Akinesia refers to a difficulty in initiating and maintaining behavior, a condition marked by slowed motor activity, a monotonous voice, and an expressionless face, resulting from taking neuroleptic drugs. Patients with Akinesia may be extremely slow to start or perform a movement, may become rapidly fatigued when performing repetitive movements, or may have problems in performing simultaneous or sequential movements.