In everyday interaction, subtle manifestations of sexism often pass unacknowledged and become internalised and thus perceived as “natural” conduct. The introduction of new vocabularies for referring to previously unnamed sexist conduct would presumably enable individuals to start problematising hitherto unchallengeable sexism. In this paper, we investigate whether and how these vocabularies empower people to speak out against sexism. We focus on the use of the term “mansplaining” which, although coined over 10 years ago, remains controversial and contested. Using Conversation Analysis and Membership Categorisation Analysis, this paper excavates the interactional methods individuals use to formulate, in vivo, some prior spate of talk as mansplaining. In doing so, speakers necessarily reformulate a co-participant’s social action to highlight its sexist nature. Accusations of mansplaining are accomplished by invoking gender (and other) categories and their associated rights to knowledge. In reconstructing another’s conduct as mansplaining, speakers display their understanding of what mansplaining is (and could be) for the purpose at hand. Thus, the paper contributes to the well-established body of interactional research on manifestations of sexism by documenting how the normativity of epistemic rights is mobilised as a resource for bringing off accusations of mansplaining.