Civilians trained as soldiers but not part of the regular army WordNet 3.0 & Open English WordNet

A militia is generally an army or some other fighting organization of non-professional and/or part-time soldiers; citizens of a country, or subjects of a state, who may perform military service during a time of need, as opposed to a professional force of regular, full-time military personnel; or, historically, to members of a warrior-nobility class. Wikipedia

Army or other fighting organization of non-professional soldiers. Wikipedia Disambiguation

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

A private force, not under government control. OmegaWiki

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. Wiktionary

Army of trained civilians called upon in time of need. Wiktionary (translation)