This article develops an identity performance model of prejudice that highlights the creative influence of prejudice expressions on norms and situations. Definitions of prejudice can promote social change or stability when they are used to achieve social identification, explanation, and mobilization. Tacit or explicit agreement about the nature of prejudice is accomplished collaboratively by persuading others to accept (1) an abstract definition of prejudice, (2) concrete exemplars of prejudice, and (3) associated beliefs about how a target group should be treated. This article reviews three ways in which prejudice can be defined in the cut and thrust of social interaction, namely, by mobilizing hatred and violence, by accusation and denial, and by repression. The struggle for the nature of prejudice determines who can be badly treated and by whom. Studying such ordinary struggles to define what counts (and does not count) as prejudice will allow us to understand how identities are produced, norms are set into motion, and populations are mobilized as social relations are reformulated.