Coun"ter*sink` . Countersinking.]
1.
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.
2.
To cause to sink even with or below the surface; as, to countersink a screw or bolt into woodwork.
© Webster 1913.
Coun"ter*sink`, n.
1.
An enlargement of the upper part of a hole, forming a cavity or depression for receiving the head of a screw or bolt.
In the United States a flaring cavity formed by chamfering the edges of a round hole is called a countersink, while a cylindrical flat-bottomed enlargement of the mouth of the hole is usually called a counterbore.
2.
A drill or cutting tool for countersinking holes.
© Webster 1913.