I do not think it means what you think it means.
One of my favorite movies of all time - perhaps the favorite - is The Princess Bride. It really has everything: action, love, fighting, humor, drama, death, triumph, ROUSes, a 6-fingered man, a giant, an albino, a pirate, and a beautiful princess.
It's also quite possible that this movie is entirely responsible for my marriage. In a good way. See, Rachel and I met on a blind date and when she asked what my favorite movie was, rather than go with Faces of Death or Girls Gone Wild, I said The Princess Bride. I think I instantly melted her heart and the rest, as they say, is history.
Anyway, about the shirt. Favorite geek outfitter, ThinkGeek, just added it to their wares. If you are a fan of the movie or know someone who is (and, frankly, that should be just about everyone), go buy one or five right now.
[Inconceivable T-Shirt]