Guerrilla. (noun)

/ɡəˈrɪlə/
/ɡəˈrɪlə/
(also guerilla)

​a member of a small group of soldiers who are not part of an official army and who fight against official soldiers, usually to try to change the government
urban guerrillas (= those who fight in towns)
guerrilla war/warfare (= fought by guerrillas on one or both sides)
a guerrilla movement
COMPARE: freedom fighter

Sounds like
gr·i·luh