Carborundum \Car`bo*run"dum\, [Carbon + corundum.]

A beautiful crystalline compound, SiC, consisting of carbon and silicon in combination; carbon silicide. It is made by heating carbon and sand together in an electric furnace. The commercial article is dark-colored and iridescent. It is harder than emery, and is used as an abrasive.

Source: Webster's Revised Unabridged Dictionary (1913)