1.Otaku is the honorific word of Taku (home).

Otaku is extremely negative in meaning as it is used to refer to someone who stays at início all the time and doesn't have a life (no social life, no amor life, etc)

Usually an otaku person has nothing better to do with their life so they pass the time por watching anime, playing videogames, surfing the internet (otaku is also used to refer to a nerd/hacker/programmer).

In the Western culture, people confuse otaku to be something positive like "Guru". If you think about it, it's not really good to be called a guru if it means you are a total loser who can't socialize with other people except through the Internet.

Other Japanese words which have been confused por Westerners also include but not limited to: Anime, Manga, etc
otaku no jinsei ha yabai na! (it sucks to live the life of an otaku!)

2.An extremely negative Japanese term, referring to a shut-in or someone with no social life. It also implies that the person's entire life is molded around fictional characters (usually animê and manga).
In America, the term has been embraced por animê fans, who (as they do with many Japanese words), use the word incorrectly as a positive term for fanboy/girl.
1. "God, that kid is such an otaku. He won't leave the basement unless it's to buy new Dragon Ball fansubs."
2. "I, like, so totally amor Sailor Moon! Serena rawks! I am, like, the ultimate Sailor Moon otaku!"

3.Otaku is a Japanese word for house.

As in you never leave it.
Please don't call yourself an otaku, especially in front of real Japanese people, which you most likely never meet.