What Does “Sexual Assault” Mean? A Century of Changing Definitions, Measurement, Reporting, and Epidemiology in the United States, 1920–2026

Objective: Every estimate of the scope of sexual victimization depends on how “sexual assault” is defined, and disagreements over definition have produced dramatically divergent statistics that continue to shape policy. This review synthesizes a century of American scholarship (1920–2026) on the definition of sexual assault, tracing changes in legal definitions, measurement instruments and national data systems, trends in police reporting, and the resulting epidemiological evidence. Methods: A narrative, evidence-based review was conducted of seminal peer-reviewed studies, national surveys, and federal statistical reports, spanning the common-law rape doctrine and early Uniform Crime Reports, the rape law reform movements of the 1970s, the rise of behaviorally specific survey measurement, the national victimization and prevalence survey infrastructure, and contemporary debates over gender-neutral, consent-based, and inclusive definitions. Results: Formal definitions of rape evolved from a narrow, gendered offense requiring force, resistance, and corroboration to broader, gender-neutral, consent-based constructs encompassing incapacitation, coercion, and non-contact violations. This expansion coincided with rising prevalence estimates, increasing police reporting over recent decades, and formal recognition of acquaintance, marital, incapacitated, and drug-facilitated rape. However, definitional plurality across legal, administrative, and research frameworks persists, generating wide variation in estimates, under-acknowledgment of victimization by survivors, and persistent attrition of cases in the criminal justice system. Conclusions: The meaning of “sexual assault” remains contested and consequential. Progress in measurement has been substantial, yet the field still lacks a single standard definition, and epidemiological surveillance and reporting reforms must continue to address gaps between legal categories, survey instruments, and victim experiences.