Bah, so paranoid! It'd most likely just get post-edited.
Don't worry about dorks; let's just get on-topic.
Yes, the most literal meaning of the word otaku in Japanese is "doesn't get out of the house much." I would say that the closest English equivalent would be "geek," or even more likely, "nerd." The main difference is that "nerd" used to refer almost completely to computer nerds. "Otaku" is a broader term.
Unlike in English-speaking fandoms, in Japan, "otaku" refers to any and all kinds of geeks who are dedicated to a certain fan following. This includes military otaku, who mainly obsess about real weaponry and warfare. In Full Metal Panic, the characters suspect that Sousuke is a military otaku. Anime otaku don't necessarily limit themselves to Japanese animation, for that matter.
Many "normal" people have a very paranoid and negative image of "otaku," because there have been a handful of cases of stalking and serial murder which made it onto Japanese news over the years. The stigma around these is similar to the many school shootings we've had in America over the years: people want to blame the hobby rather than the person. I've found that Japanese women in particular, especially those without teenage sons, have had little exposure to hobby culture and are especially paranoid about it. Some Japanese teachers in America, however, know that they have anime to thank for the surge in interest in the Japanese language, and go along with it. At my university they even started a class based on learning Japanese through anime.
Anyway, for a pretty accurate all-encompassing definition of what "otaku" means to the Japanese, watch a few episodes of Genshiken; an anime about a quintessential cross-genre college otaku club. Yes, it DID use to mean something pretty bad, but Japanese otaku are starting to say "screw you; I'm different and I'm proud." I'm not sure whether they're being inspired by American fans, or not, but Japanese subculture has strengthened itself over the years, thanks in no small part to the internet. ^_^
When I came back from Japan, I felt weird about using the term "otaku," since I'd learned the difference between their use of the word and ours. But really, it's the stigma around a word that defines what it means, NOT some dictionary somewhere. If Americans use the word to mean "anime fan," then the English definition of it will
become "anime fan." Japanese has done the same to imported words from our language, such as "gothic lolita" and even "cosplay." The only time you should be careful of your use of the word "otaku" is when you are actually in Japan, or when talking to "uninitiated" Japanese locals. Otherwise, don't worry about it, okay? ^_^
