Heater \Heat"er\ (h[=e]t"[~e]r), n. 1. One who, or that which, heats. [1913 Webster] 2. 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. [1913 Webster] 3. A pistol or other carryable firearm; as, gunmen with their heaters bulging in their pockets. [slang] [PJC] {Feed heater}. See under {Feed}. [1913 Webster]