- arsonist arsonist n.
1. 1 a criminal who illegaly sets fire to property.
Note: The definition of this crime is varied by statues in different countries and states. The English law of arson has been considerably modified in the United States; in some of the States it has been materially enlarged, while in others, various degrees of arson have been established, with corresponding punishment. --Burrill. [1913 Webster]
The Collaborative International Dictionary of English. 2000.