To chamfer or form a depression around the top of (a hole in wood, metal, etc.) for the reception of the head of a screw or bolt below the surface, either wholly or in part; as, to countersink a hole for a screw.
- A hole with the top part enlarged so that the head of a screw or bolt will lie flush with or below the surface.
- A tool for making such a hole.
- To make a countersink on or in.
- To drive (a screw or bolt) into a countersink.