commando

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A small fighting force specially trained for making quick destructive raids against enemy-held areas.
• noun A member of such a force.
• noun An organized force of Boer troops in South Africa.
• noun A raid made by such a force.
• idiom (go commando) To wear clothing without wearing undergarments, especially underpants.

from The Century Dictionary.

• noun The enrolled militia of an electoral district in the late Dutch republics of South Africa.
• noun A unit of the Boer army commanded by an officer whose title was Commandant.
• noun A military expedition or raid undertaken by private individuals for personal ends; more specifically, the name given to the quasimilitary expeditions undertaken by the Boers and English farmers of South Africa against the natives.

from the GNU version of the Collaborative International Dictionary of English.

• noun In South Africa, a military body or command; also, sometimes, an expedition or raid.
• noun a usually small military unit trained to perform special missions, often behind enemy lines, and usually employing hit-and-run tactics. Such units often have the destruction of fixed targets, such as enemy installations, as their mission, in contrast to normal combat units which engage the enemy army directly.
• noun a member of a commando{2} unit.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A small fighting force specially trained for making quick destructive raids against enemy-held areas
• noun A commando trooper
• noun historical An organized force of Boer troops in South Africa; a raid by such troops

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun an amphibious military unit trained for raids into enemy territory
• noun a member of a military unit trained as shock troops for hit-and-run raids