What does this symbol mean?

I've seen this symbol a lot, especially in Japanese tattoos, it looks like the silhouette of a flower with a swirl in the center. I was curious as to what it meant. Is there a specific name or story behind the symbol? Here's an image of an MMA fighter who has it tattooed on his shoulders for reference - http://mmajunkie.com/dyn/images/fighters/javier-torres.jpg