countersink Meaning, Definition & Usage

noun a hole (usually in wood) with the top part enlarged so that a screw or bolt will fit into it and lie below the surface
noun a bit for enlarging the upper part of a hole
counterbore; countersink bit.
verb insert (a nail or screw below the surface, as into a countersink)
set.

imperfect & past participle Countersunk present participle & verbal noun Countersinking

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.
To cause to sink even with or below the surface; as, to countersink a screw or bolt into woodwork.

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 conterbore.
A drill or cutting tool for countersinking holes.