rebelling against the ruling authority
An insurgent militia now controls the northeastern corner of the state.
in (against)#surgere (to rise) (Latin)
in (not)+surgen (surgeon). SURGEON people obey rules in the hospital and during operation. But INSURGEON people does not obey rules a person (army man) who does not listen to the command of his sergeant is rebellious in nature therefore in-surgent = one who does not listen to his sergeant [ commander] thus is rebellious.