the entire body of physically fit civilians eligible by law for military service
"their troops were untrained militia"
"Congress shall have power to provide for calling forth the militia"
An army of trained civilians, which may be an official reserve army, called upon in time of need, the entire able-bodied population of a state which may also be called upon, or a private force not under government control.
"The local militia gathered at dawn to reinforce the border defenses before the main army could arrive."