Categories are not invariant. This paper attempts to explore the dynamic nature of semantic category, in particular, that of fashion language, based on the cognitive theory of Dawkins’ memetics, a new theory of cultural evolution. Semantic attributes of linguistic memes decrease or proliferate in replication and spreading, which involves a dynamic development of semantic category. More specifically, it is committed to unveiling the dynamic categorization of semantic category of fashion language through analyses of different lexical memes, sentence memes, and discourse memes. It is found that: (I) the replication and spreading of linguistic memes are closely related to the dynamic categorization of semantics, i.e., the stability of semantic categories is maintained by the replicability of memes, and the dynamic nature of semantic categories is determined by the evolution tendency of memes; (II) the underlying working mechanisms for meme variation and mutation are metaphor and metonymy; (III) how memes replicate and vary plays an important role in dynamic categorization of semantics of fashion language.