Definition of Ego

I; myself. This term is used in forming genealogical tables, to represent the person who is the object of inquiry.

The part of the conscious personality which has the task of balancing the demands of the real world and maintaining harmony between the id (instinctual drives) and the superego (morality of the conscience); that portion of the total personality noticeable to others which maintains contact with the environment of the outer world.

See also Alter ego.

That's the definition of Ego in Black's Law Dictionary 6th Edition. Courtesy of