Submitted by S.P. Sullivan:
The tattoo is Kurt Vonnegut's trademark "backdoor."
I got this when I turned eighteen because I wanted to do something stupid and impulsive, but not entirely uncharacteristic of me. My father introduced me to Vonnegut; the first thing he said when he saw it was "you know that's a sphincter, right?"
I've grown tired of explaining it to people, mostly because they usually look at me like I'm insane. So, when asked, I inquire to the inquirer, "Have you read Vonnegut?" If yes, it's relatively easy to explain. If no, I just say it's an asterisk and leave it at that. I'm often asked if it's a botched attempt at the Red Hot Chile Peppers logo. So it goes.