Social innovation is often appointed as an essential part of agricultural and rural innovation. Everybody seems to agree that social innovation is important but what exactly is meant by the term remains often unclear. This paper aims at clarifying the meaning and significance of the concept by going back to its root in innovation science and policy. It appoints three main interpretations of social innovation, referring to the social mechanism of innovation, the social responsibility of innovation and the need for innovating society. Studying its application in the field of agriculture and rural development reveals that social innovation is rarely referred to when agriculture as a singular economic activity is concerned, but prominently present in discussions about rural development. Here social innovation may be referred to when identifying society’s need for more sustainable production methods, the necessity for collaboration and social learning, and the scope of change needed for revitalising (rural) society. Often, however, social innovation is presented as a tangle of interdependent processes and beneficial outcomes. Its fuzziness contributes to its discursive power in discussions about agricultural politics and the significance of sustainability, but also hides the valued-loadedness of social innovation. As a result its critical potential becomes neutralised. For gaining more insight in how to more effectively support social innovation, it is important to disentangle the social innovation jumble, to unravel the diverse interrelations and to explore and monitor its functioning and contribution to processes of social change and renewal.