As the discussion of neology has expanded, various vocabulary and expressions have been added to the category of neology. Thus, the category of neology has been expanded. In this study, we propose ‘trending expressions’ as a broader concept than ‘neology’ or ‘memes’, which are the subject of today’s research. Accordingly, we define trending expressions based on the common characteristics of trending expressions and classify them according to their types. The most basic characteristic of trending expressions is ‘virality’, which means that they have a certain level of public recognition. In addition, trending expressions that are popular today are usually ‘deviant’ in the sense that they deviate from existing expressions, linguistic norms, or common sense in order to achieve novelty, and the deviant nature of trending expressions gives some trending expressions a cryptic character. Finally, these expressions are ‘playful’ in the sense that the use of language in and of itself creates a sense of satisfaction for the speaker. In this study, we categorize trending expressions into word-level trending expressions, phrase-level trending expressions, sentence-level trending expressions, sentence-plus trending expressions, and phrase-plus trending expressions according to their size, and provide examples of trending expressions belonging to each type. In addition, according to the kind of meaning they have, trending expressions are categorized into those that indicate new concepts, those that have specific discourse functions, and those that are simply used for entertainment.