A large stone or brick placed at the back of a fireplace to reflect heat forward into a room.
Compound of 'back' (Old English 'bæc') + 'stone' (Old English 'stan'). This architectural term emerged when builders discovered that backing materials could increase heating efficiency.
Medieval masons realized that a backstone could double the heat radiating into a room—a clever bit of thermodynamics that made the difference between freezing and surviving harsh winters!
Complete word intelligence in one call. Free tier — 50 lookups/day.