Guerrilla refers to a type of fighter or fighting that uses surprise attacks, quick strikes, and clever tactics instead of traditional warfare. Guerrilla fighters are usually smaller groups fighting against a larger, more powerful army. Instead of meeting their enemy in open battle, they might ambush supply convoys, sabotage equipment, or strike quickly and then disappear into forests or mountains.

The word comes from Spanish, where it means “little war.” Guerrilla tactics have been used throughout history by groups who couldn't match their opponents in size or firepower. During the American Revolution, colonial militias used guerrilla tactics against British forces, hiding behind trees and rocks instead of marching in formation. In the 1800s, Spanish fighters used guerrilla warfare against Napoleon's invading army.

The approach relies on knowing the local terrain better than the enemy, moving fast, and avoiding direct confrontation. A guerrilla force might control the countryside at night but vanish during the day. They make themselves hard to find and harder to fight.

People sometimes use guerrilla in other contexts, like guerrilla marketing, which means unconventional, surprise advertising tactics that catch people's attention in unexpected ways. But the core idea remains: small, nimble, and surprising rather than large and conventional.

As an adjective, guerrilla describes these tactics or groups, as in guerrilla warfare or guerrilla fighters.