Federal law, 22 U.S.C. §. 2656f(d), defines "terrorism" as "premeditated, politically motivated violence perpetrated against noncombatant targets by sub-national groups or clandestine agents."

This is consistent with the common American understanding of the term, as reflected in the American Heritage Dictionary of the English Language [4th ed.,2000] definition of "terrorism" as "the unlawful use ... of force or violence by a person or an organized group against people or property with the intention of intimidating or coercing societies or governments, often for ideological or political reasons."

Based on U.S. law, the State Department has formally designated Hamas, Islamic Jihad, PFLP and Al Aqsa Martyrs Brigades as "foreign terrorist organizations."

The FBI defines terrorism as, "the unlawful use of force or violence against persons or property to intimidate or coerce a government, the civilian
population, or any segment thereof, in furtherance of political or social objectives."

The FBI further classifies terrorism as either domestic or international, depending on the origin, base and objectives of the terrorist organization.