generally refers to an army or other fighting force that is composed of non-professional fighters

A militia is a group of people who are not in the standing army or regular military but do many military tasks such as collecting weapons, training soldiers, defending people or land and policing an area. Militias are often made up of veterans, who used to be in the military.

Captain John Parker, a militia leader of during the American Revolutionary War

Some militias, like the United States National Guard, are organized by a government. It is a group of state militias that help with wars, natural disasters and other emergencies. Others are not connected to a government and may even be illegal. One common definition of a militia includes all men who can serve as soldiers.

In the early late 20th century, some militias acted as professional forces but were still "part-time" or "on-call" organizations.