Technically, the word was thirteen letters long, but that's because I used the adjective form ending in "ing" instead of the noun form ending in "er".
And it isn't that I rarely use it. As The Socialist will only be too happy to tell you, I never use it. I find it offensive. The poor man is far more free with his vocabulary than I am, and it drives him batty when I berate him for using a few words that I find especially vile.
But then again, that "M"-word-that-I-never-use idiot hit my Prius. If that occasion didn't call for an especially vile word, then nothing does.