a member of an unofficial military group that is trying to change the government by making sudden, unexpected attacks on the official army forces

A small band of guerrillas has blown up a train in the mountains. 一小队游击队员炸毁了山区的一列火车。

guerrilla warfare 游击战

using unusual methods to create or get attention for your ideas, art, products, etc., usually ones that cost little money and involve using public spaces

He films on the streets, with a tiny budget - this is guerrilla film-making.

A new work by the "guerrilla" artist known as Banksy has appeared.