IPA: /ɪnˈsɜːrdʒənsi/
KK: /ɪnˈsɜr.dʒən.si/
A situation where a group of people rises up against a government or authority, often in a violent way, but is not as organized as a full revolution.
The country faced a serious insurgency that challenged the government's control.
Insurgency is formed from "in-" (meaning against) and "surgere" (meaning to rise). The term describes a movement that rises up against an established authority or government.
Think of a movement that 'rises up' ('surgere') 'against' ('in-') something, which helps you remember that insurgency refers to a rebellion or uprising.