Recent research suggests the observation or imagination of somatosensory stimulation in another (e.g., touch or pain) can induce a similar somatosensory experience in oneself. Some researchers have presented this experience as a type of synaesthesia, whereas others consider it an extreme experience of an otherwise normal perception. Here, we present an argument that these descriptions are not mutually exclusive. They may describe the extreme version of the normal process of understanding somatosensation in others. It becomes synaesthesia, however, when this process results in a conscious experience comparable to the observed person's state. We describe these experiences as 'mirror-sensory synaesthesia'; a type of synaesthesia identified by its distinct social component where the induced synaesthetic experience is a similar sensory experience to that perceived in another person. Through the operationalisation of this intriguing experience as synaesthesia, existing neurobiological models of synaesthesia can be used as a framework to explore how mechanisms may act upon social cognitive processes to produce conscious experiences similar to another person's observed state.