This article examines the concept of slave labour through two case studies from Brazil. One involves internal migrant workers and the other cross-border migrant workers. There have been accusations of slave labour in both cases. I argue that slave labour is a multi-dimensional concept and that cognate notions (eg forced and unfree labour) could also be reconceived as multi-dimensional. Recent works have proposed that a continuum viewing labour relations as more or less free should replace dichotomies such as free vs unfree. I argue for taking this further to recognise, first, that workers may be more or less free in different ways, and second, that the resulting conditions of employment can be characterised as more or less degrading, also in different ways. This multi-dimensional approach allows for a better understanding of the heterogeneity of apparently unfree labour relations and for greater recognition of the agency of workers labelled as slaves.