This design is called an Enso Circle and is one of the central symbols of Zen. Done by Denis of the Aloha Tattoo Sutdio in Karlsruhe in South Germany, the rendering of the design is really captured well.
It is supposed to look like a brush drawing and is meant to have the ends not quite meet. Wikipedia offers this definition on the symbolism: “Ens is perhaps the most common subject of Japanese calligraphy, symbolizing enlightenment, strength, elegance, the universe, and the void; it is also an “expression of the moment” and thus is often considered a form of expressionist art.”
The natural brush stroke is apparent with the dense point on the left the clear starting point, fanning out and ending with the more sparse brush trail ending on the right. When you know that it is supposed to represent a brush drawing, it is really beautiful and well executed.