Množina: arsons

ETYM Old Fren. arson, arsun, from Latin ardere, arsum, to burn.
Malicious burning to destroy property; SYN. incendiarism, fire-raising.
Malicious and willful setting fire to property.
Often arson is a crime committed to claim insurance benefits fraudulently.
The willful or malicious burning of property (as a building) especially with criminal or fraudulent intent.

Množina: arsonists

A criminal who illegally sets fire to property; SYN. incendiary, firebug.