3,000 years of feminine anger...
The average person only knows the basics about Medusa; That she was a "monster" with snakes for hair, and who turned people to stone who dared to gaze upon her.
She was far, far more than that, which is why she remains a powerful symbol for women even in modern times.
In Greek mythology, she was a beautiful, young and devoted priestess of the Temple of Athena. She was a chaste maiden -- virginal and pure by the required standards of a priestess to her goddess. However, things went sour for Medusa when she was raped by Poseidon -- the Olympian god of the sea. Two cardinal violations were made on this day: Medusa's virginity and sexual autonomy were stolen from her, as was the sacred purity from Athena's temple. Because of this, Medusa was punished harshly by her goddess -- and she was cursed with a truly cruel version of eternal life. While the cursed woman would live forever, she would do so alone -- and anyone who looked upon her face would immediately turn to stone. Medusa was then banished by Athena to live at the "farthest edge" of the earth with her two blind Gorgon sisters. That is where she remained, until she was slain and beheaded by the hero Perseus.
In most versions of the myth, Medusa is transformed physically by the rape of Poseidon. She becomes hideous and loses all semblance of her feminine desirability. She becomes a monster, and even though she lives essentially alone -- and seeks not to harm those who live beyond the shadows of her isolated home -- she becomes the prized trophy of bloodthirsty men who have only one goal: To destroy her.
Medusa's severed head was used as a weapon, and then ultimately given back to the goddess Athena, who placed it upon her shield. In a way, it was because of this final, and strangely honorable act, that the symbolism of Medusa became positive and powerful.
Medusa symbolizes protection -- especially protection over women from violence.
Medusa symbolizes justice.
Medusa symbolizes raw feminine anger.