The phrase "set fire to" is a commonly used expression that refers to intentionally causing a fire. However, there are various synonyms that can be used to describe this action. Some of the commonly used ones include "ignite", "kindle", "light up", "spark", "torch", "burn", "flare up", "enflame" and "incinerate". Each of these words carries its own unique connotations and can be used depending on the context of the sentence. It is always essential to choose synonyms carefully as they can change the tone and the meaning of a sentence significantly. However, regardless of the synonym you choose, intentionally setting fire to anything can be both dangerous and illegal in many cases.