With Internet users constantly participating in online interactions, a wide range of novel usages have emerged, some of which involve multi-word expressions. The use of multi-word expressions in online discourses (e.g. their syntagmatic patterns and communicative functions) has not been fully explored. Therefore, this study sets out to investigate the Chinese word string bù shuō le ‘not talk anymore’, which occurs much more frequently in online discussion boards than in other written or spoken modes. In the corpus-based analysis, multiple contexts in which bù shuō le indicates a reluctance to further elaborate are identified. The most common context is that the writer recounts a face-threatening experience and uses bù shuō le to bring the post to the conclusion, express a casual attitude toward that experience, and exert a humorous effect. This study contributes additional evidence that demonstrates how multi-word expressions fulfill textual, expressive, and interpersonal functions in online discourses.