multibyte character
A character encoded using two or more bytes, as opposed to a single-byte character. Common in discussions of East Asian character sets.
Japanese kanji are represented as multibyte characters.
multibyte encoding; variable-width encoding
An encoding scheme where characters can occupy a variable number of bytes. Often contrasted with fixed-width encodings. Sense 3 (variable-width encoding) is a closely related concept and is merged here.
UTF-8 is one type of multibyte character encoding.