Onomatopoeia is typically described as involving the use of words which imitate sounds. The study of onomatopoeia is often approached through theories of sound symbolism. However, while such approaches provide rich descriptions of onomatopoeia, they have generally paid little attention to the role of onomatopoeia in communication. In this study, we focus on onomatopoeia as a communicative phenomenon, considering what the use of onomatopoeia communicates, and how it is communicated. Our main claim is that onomatopoeia falls on the showing--saying continuum (Wharton, 2009), and involves elements of both showing and saying, contributing to relevance by providing direct evidence for some of the meaning it communicates. We argue that onomatopoeia involves the exploitation of resemblances, and that the non-arbitrary relationship between sound and meaning is a result of the communicator’s attempts to recreate his sensory experience using sounds which provide a faithful enough representation of his experience. What is communicated by the use of onomatopoeia is both vague and context-dependent: it amounts to what relevance theorists call an impression rather than a determinate meaning. Our analysis also extends to multimodal and cross-modal communicative behaviours and should therefore pave the way for further investigation of the interface between verbal and non-verbal communication.