The term "autonomous ego" was coined by the proponents of ego-psychology.
According to the proponents of ego-psychology, the ego becomes autonomous by achieving a harmonious balance between its primitive drives and the dictates of reality.
The autonomous ego is thus synomymous with "the strong ego," "the well-adapted ego," "the healthy ego."
Psychoanalysis was conceived of by the proponents of ego-psychology as the process of helping the analysand ego to become autonomous: this was supposed to be achieved by the identification of the analysand with the strong ego of the analyst.
Lacan is very critical of the concept of the autonomous ego.
He argues that the ego is not free but determined by the symbolic order.
The autonomy of the ego is simply a narcissistic illusion of mastery.
It is the symbolic order, and not the ego, which enjoys autonomy.