Heater /(hēt"ẽr)/

Heat·er

Heater

One who, or that which, heats.
Any contrivance or implement, as a furnace, stove, or other heated body or vessel, etc., used to impart heat to something, or to contain something to be heated.
A pistol or other carryable firearm; as, gunmen with their heaters bulging in their pockets. [slang]