What does it mean to be “a god”?

There are stories, legends, mythologies, folklore, traditions, histories, scriptures, and texts from all around the world which tell us of humans who have reached the stature of the gods. They have, in essence, become "a god." Some recognizable examples are people such as Jesus, Siddhartha Gautama (Buddha), and Muhammad. The process that these went through has been called theosis, deification, divinization, realization, awakening, and enlightenment. What does it mean to become or be "a god"?