| 1. | a closed vessel or arrangement of vessels and tubes, together with a furnace or other heat source, in which steam or other vapor is generated from water to drive turbines or engines, supply heat, process certain materials, etc. Compare fire-tube boiler, water-tube boiler. |
| 2. | a vessel, as a kettle, for boiling or heating. |
| 3. | British. a large tub in which laundry is boiled or sterilized. |
| 4. | a tank in which water is heated and stored, as for supplying hot water. |