- to enlarge the upper part of (a cavity), especially by chamfering, to receive the cone-shaped head of a screw, bolt, etc.
- to cause (the head of a screw, bolt, etc.) to sink into a prepared depression so as to be flush with or below the surface.
- a tool for countersinking a hole.
- a countersunk hole.
- to enlarge the upper part of (a hole) in timber, metal, etc, so that the head of a bolt or screw can be sunk below the surface
- to drive (a screw) or sink (a bolt) into such an enlarged hole
- a tool for countersinking
- a countersunk depression or hole
