The September 11th terrorist attacks refer to a series of coordinated suicide hijackings carried out by terrorists on September 11, 2001. Four airplanes were used as weapons, resulting in thousands of lives lost and significant damage to buildings, including the Twin Towers in New York City.
Related terms
Patriot Act: The Patriot Act is legislation enacted after 9/11 that expanded government surveillance powers in order to prevent future terrorist attacks.
Department of Homeland Security (DHS): DHS was established after 9/11 as part of an effort to protect the United States from terrorist attacks and respond to natural disasters.
Transportation Security Administration (TSA): TSA is an agency of the DHS responsible for security at airports and other transportation systems in order to prevent terrorist attacks.