Yeah, you read that right. And no, if you don't already know what it is, I'm not telling you. Go to Wikipedia if you're so curious.
There are no details about how Matsui sustained his injury, other than it took place on no less than St. Patrick's Day. Obviously the luck of the Irish was not with him that day. And, just as obviously, the Astros training staff may want to invest in some extra soft Charmin in the coming days.