Understanding the import of laughter, has interested philosophers and literary scholars for millennia and, more recently, psychologists, biologists, neuroscientists, and linguists. However, the assumption has been that laughter lacks meaning akin to what words and phrases possess and that it does not contribute to the compositional construction of meaning. In this paper, we argue that, in fact, laughter (and other non-verbal social signals like smiling, sighing, frowning) has propositional content—it involves reference to external real world events, has stand alone meanings, and participates in semantic and pragmatic processes like repair, implicature, and irony. We show how to develop a formal semantic and pragmatic account of laughter embedded in a general theory of conversational interaction and emotional reasoning and show how to explain the wide, indeed in principle unbounded range of uses laughter exhibits. We show how our account can be extended to other non-verbal social signals like smiling, sighing, eye rolling, and frowning. Should laughter and its ilk be incorporated in the grammar? We suggest that they probably should be, if one assumes a conversationally–oriented view of grammar. But various open issues remain.