This is a word normally used for the attempt to convey Japanese in a written form using the western or roman alphabet. It is basically a phonetic conversion of the spoken language which of course means that it can have variant spellings.

Sensei has pointed out to me that Romanji itself has a perfectly acceptable (and I think more commonly used in Japan) alternate spelling of Romaji (I suspect the Japanese do not pronounce the "N" of Roman). For more details on all this see Jeeves' nodes on the Japanese language particularly Japanese romanization and Hepburn.

Correct written Japanese consists of three alphabets:
  • Kanji: A pictographic alphabet of about 2000 common characters (and a lot more uncommon ones) used to represent common concepts and names.
  • Hiragana: A cursive phonetic alphabet normally used to spell out words with a Japanese basis if they have no Kanji or a rare Kanji. These are also sometimes used to write the phonetic version of a Kanji beside the Kanji in books for younger children to help them learn the Kanji.
  • Katakana: An angular phonetic alphabet (with the same set of characters/sounds as Hiragana) that is normally used to spell out non-japanese words. I believe it can also be used for emphasis.