Prejudice, stereotyping, or discrimination on the basis of sex or gender — and, in its analytically richer use, the structured social arrangements that systematically produce such prejudice and discrimination as ordinary outputs. The word entered American English in the 1960s, coined on the model of racism by second-wave feminist writers who needed a term to name what prejudice against women failed to capture: not only individual attitudes but a comprehensive social system.
The conceptual move parallels the development of the analytic vocabulary of race: from individual prejudice ("some people are sexist") to institutional and structural analysis (gendered wage gaps, the unequal distribution of unpaid care work, gendered patterns in legal treatment of violence and consent, the cultural construction of competence as masculine). Sexism in this fuller sense is the everyday operating system of Patriarchy — the routine mechanisms through which gender hierarchy is reproduced, often by people who do not consciously hold sexist beliefs.
Intersectional analysis insists that sexism is never experienced in isolation: the sexism a Black woman faces is structurally distinct from the sexism a white woman faces, and from the racism a Black man faces. Pauli Murray's term Jane Crow — coined in the 1940s to describe the compounded subordination of Black women — was an early articulation. bell hooks has argued that sexism is not only a structure that harms women; it deforms men as well, by demanding the suppression of capacities for care, vulnerability, and connection that are constitutive of full human life.