In automata theory, the class of unrestricted grammars (also called semi-Thue, type-0 or phrase structure grammars) is the most general class of grammars in the Chomsky hierarchy.

Estimate without any imposed limitations.

a type of naval warfare in which submarines sink merchant ships such as freighters and tankers without warning.

Unrestricted Warfare: Two Air Force Senior Colonels on Scenarios for War and the Operational Art in an Era of Globalization is a book on military strategy written in 1999 by two colonels in the People's Liberation Army, Qiao Liang and Wang Xiangsui.

An unrestricted line officer (shortened to URL officer) is a designator given to a commissioned officer of the line in the United States Navy, who is eligible for command at sea of the navy's warfighting combatant units such as warships, submarines, aviation squadrons and SEAL teams.