Otaku

[Sarah]

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 home all the time and doesnt have a life (no social life, no love life, etc)
Usually an otaku person has nothing better to do with their life so they pass the time by 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, its not really good to be called a guru if it means you are a total loser who cant socialize with other people except through the Internet.
Other Japanese words which have been confused by Westerners also include but not limited to: Anime, Manga, etc

[Donald Trump]

The term otaku seems to have been introduced to anime fans in the US and other countries via Studio Gainaxs Otaku no Video 1985, a self-parody film.
Otaku, meaning probably venerable house, refers to someone who has a devotion to a subject or hobby (not necessarily anime) to the point of not leaving home. For instance, an otaku fan of a particular movie star could quite possibly know all of the films s/he has been in, their birth date, time of birth, shoe size, favorite toothpaste, etc. Generally speaking, calling someone an otaku in Japan is an insult, implying that their social skills have atrophied or never even developed, due to their manic involvement in their chosen fandom.
In America, the term is used to denote a zealous fan, usually of anime and/or manga. Due to its introduction to most peoples vocabulary through its tongue-in-cheek use in Gainaxs film, otaku tends to have a much less dire definition overseas.
When dealing with Japanese people, however, it may be best to keep in mind the modern Japanese image of an otaku -- Someone who only leaves their home to eat or shop, if at all, with an overwhelming and unhealthy obsession about something. It can as easily refer to a stalker or sociopath as it can to a harmless anime buff.
Best to avoid the word altogether if one is not sure of the context in which it will be received.

[Mark Zuckerberg]

A Japanese word describing a person beyond the realm of fandom but into mania that is improperly used by American fans.
In Japan the word otaku has become taboo because of Miyazaki Tsutomu who went on a toddler murdering spree in the 80s, video taping the young girls he had murdered from an obsession with lolicon (female pedophilic manga).
Americans use this term to call themselves fanboys or fangirls with almost no knowledge of the horrific roots behind the word.

[Little_Girl]

My definition, which was correct was removed by biased peoples. Oh well. Here I go again.
In Japan the word Otaku is a label that is quite bad. Most Japanese people would not want to be considered an otaku.
In America, however, we have morphed the word as we always do to our own meaning. There is nothing wrong with this. Over in America it means to be a big fan of, and really doesnt have a bad meaning, as it would in Japan.
As such, you wouldnt want to go to Japan and start saying how much of an Otaku you are. In America this is fine, and probably in Canada as well. However, alot of people here seem to forget that they are saying what the Japanese interpret it as. Most people that read this hail from North America where the definition has a fairly benign meaning.
I rest my case.

[Becky]

JAPAN:In [Japanese] was Otaku very polite form of you (literally your house). During the time the meaning has changed to hardcore fan of something usually [manga] and [anime]. Otaku has became used in meaning : nerd or jerk. Nowadays in Japan is the meaning returning back to non-offensive usage because of econimic trends.

ELSEWHERE: Out of Japan is the term Otaku used in the meaning of hardcore fan of anime and Manga. Many of anime fans call themselves otaku despite knowing its meaning in Japan.

[Sarah]

An extremely negative Japanese term, referring to a shut-in or someone with no social life. It also implies that the persons entire life is molded around fictional characters (usually anime and manga).
In America, the term has been embraced by anime fans, who (as they do with many Japanese words), use the word incorrectly as a positive term for fanboy/girl.

[Rihanna]

Japanese: An insulting word meaning someone who is completely obsessed with something. They are the type that generally live in their parents basements at 30 years old and have no social life.
English: A term meaning someone very into anime/manga/Japanese culture. It can be taken as either a compliment or an insult, depending on the recipient (I take it as a compliment, for example).

[Couch Potatoe]

Otaku in japanese is used primarily to describe someone who is obsessed with something to the point of un-healthiness. They lose their grip on reality so to speak. Gun-Otaku, one who is obsessed with guns. porn-otaku, one obsessed with porn. so on and so forth. The american meaning, maybe its used else where to...I dunno. any way, otaku over here is someone who likes anime a wwhhoollee lot, though they normally lead a normal life (unlike jap. otaku). Not really a bad term, though many see it as such.