A more thorough explanation:

Definition: An incendiary is a person who intentionally and illegally sets fire to property. It can also refer to an object, such as a bomb or chemical agent, that is designed to start a fire.

Examples:

• John was arrested for being an incendiary after he was caught setting fire to his neighbor's shed.
• The police found evidence of incendiary devices at the scene of the fire.

The first example illustrates the definition of an incendiary as a person who sets fire to property. John intentionally started a fire, making him an incendiary. The second example shows how incendiary can also refer to an object, as the police found evidence of a device designed to start a fire.