Definitions for z-variant
(Unicode) a shape variant of a Han character, encoded for historical reasons.
Origin: z (axis) + variant; from the three dimensions visualized for the character space. The x-axis separates characters by semantics (function and meaning, e.g. A from B), the y-axis separates them by their general form (abstract shape, e.g. A from a), and the z-axis by their actual shape (minor details such as typeface, e.g. a from a).
In Unicode, two glyphs are said to be Z-variants if they share the same etymology but have slightly different appearances and different Unicode codepoints. For example, the Unicode characters U+8AAA 說 and U+8AAC 説 are Z-variants. The notion of Z-variance is only applicable to the “CJKV scripts” — Chinese, Japanese, Korean and Vietnamese — and is a subtopic of Han unification.