When referring to Native populations, "decimated" means that a large percentage of the population was killed or wiped out. In this context, it specifically refers to the devastating impact of diseases brought by Europeans, which resulted in a significant decline in Native American populations.
Related terms
Epidemic: An outbreak of disease that spreads quickly and affects a large number of people within a short period of time.
Smallpox: A highly contagious and often fatal disease caused by the variola virus, which had a devastating impact on Native American populations during European colonization.
Colonization: The process by which one country establishes control over another territory for economic or political purposes. During colonization, Europeans brought diseases that had unintended consequences for Native Americans.