English

Noun

gaiji ‎(plural gaiji)

1. A character that is valid in a given writing system, but that is not included in the present font and/or the present character encoding, and which therefore is displayed using an additional mechanism.^[1][2] Mutually distinct from tofu and from mojibake.

References

1. ↑ https://www.w3.org/International/articles/missing-char-glyph/index.en
2. ↑ http://glyphs.webfoot.com/blog/2011/03/19/gaiji/

Japanese

Romanization

gaiji

1. rōmaji reading of がいじ