full-width character
Computing term for a character that occupies two standard-width positions, typical of CJK and certain symbols in JIS, Unicode, etc. Contrasts with 半角文字 (half-width character).
See also: 半角文字
Full-width characters are displayed at twice the width of half-width characters.
パスワードには全角文字を使わないでください。
Please do not use full-width characters in your password.
半角文字 is a half-width character, occupying one standard-width position, commonly used for ASCII and single-byte characters.
Compound of 全角 (full-width) + 文字 (character). The term 全角 originates from typesetting, where a full-width character occupies a square em-box.