Wiktionary
circular definition
n. (context semantics English) A definition relying directly or indirectly on the term being defined.
Wikipedia
Circular definition
A circular definition is one that uses the term(s) being defined as a part of the definition or assumes a prior understanding of the term being defined. There are several kinds of circular definition, and several ways of characterising the term: pragmatic, lexicographic and linguistic.
Usage examples of "circular definition".
Vicki asked, playing the circular definition of her vision over his face.