That tattoo is a unicersal hexagram designed by Aliester Crowley.http://en.wikipedia.org/wiki/Unicursal_hexagram
From Wikipedia, the free encyclopedia
The unicursal hexagram is a hexagram or six-pointed star that can be traced or drawn unicursally, in one continuous line rather than two overlaid triangles. The hexagram can also be depicted inside a circle with the points touching it.
The unicursal hexagram is used to express a high level of self-confidence and belief that one can achieve the highest of goals and become a divine figure.
Aleister Crowley's adaptation of the unicursal hexagram placed a five petaled rose, (symbolizing the divine) in the center; the symbol as a whole making eleven (five petals of the rose plus six points of the hexagram), the number of divine union.
It is also used in the Greek and Hindu mythologies. as a symbol of dedication to the divine rulers.
A unicursal hexagram is also seen as a symbol of the solar system in some Pagan philosophies, with the central intersection representing the sun and the outer intersections and points representing the celestial bodies.
 Popular culture
* British artist Paul DeGarmo is known for his paintings featuring unicursal hexigrams.
* The unicursal hexagram was part of the symbol called "The Seal of Orichalcos" that was prominent in the Waking the Dragons arc of Yu-Gi-Oh! In fact, one of the antagonists of the arc is named Allister, referencing the famous occultist Aleister Crowley.
* A unicursal hexagram appears several times in the TV series Supernatural as a symbol to ward off evil entities.
* Danny Carey, the drummer from the progressive rock band Tool, features the unicursal hexagram in some of his imagery, and configures his drum kit in this arrangement as well.
* The members of Polish blackened death metal band Behemoth all wear pendants of unicursal hexagrams as part of their stage outfits.
* In one season of the anime Yu-Gi-Oh!, the universal hexagram was used in the artwork of the card "The Seal of Oreikalchos".