Autonomy refers to the ability to function independently without control by others. "Function" includes actions, decisions and behaviour.
Other /More definition:
Autonomy refers to the capacity to make decisions independently, to serve as one's own source of emotional strength, and to otherwise manage one's life tasks without depending on others for assistance; an important developmental task of adolescence.
Autonomy is also defined as the ability to behave independently, to do things on one's own.