What is the meaning of Guerrilla?

A soldier in a small independent group, fighting against the government or regular forces by surprise raids.

A non-official war carried out by small independent groups; a guerrilla war.

Relating to, using, or typical of guerrilla warfare, or its principles of small independent or non-official perpetrators.

Relating to, using, or typical of guerrilla marketing.

Using unconventional, non-traditional, non-mainstream and often subversive practices to achieve something.

guerrilla (small official or unofficial military troop)

guerrilla war

a guerrilla war; guerrilla warfare

a guerrilla fighter

guerrilla (small official or unofficial military troop)

guerrilla war

guerrilla (small official or unofficial military troop)

guerrilla war

Source: wiktionary.org