1. a person who has a compulsion to set fires; an arsonist
Usage: informal; often used in clinical or psychological contexts
2. a firework or pyrotechnic device
Usage: informal; slang

Examples

• The fire investigator suspected a pyro was responsible for the series of arsons.
• The police arrested a known pyro after finding evidence at the scene.
• Kids set off pyros in the parking lot on the Fourth of July.
• The festival banned pyros after a safety incident last year.
• A pyro with a history of fire-setting was monitored by authorities.