Countersink /(koun"tẽr*sĭṉk`; 277)/

Coun·ter·sink

Countersink

v. t.

imp. & p. p. Countersunk; p. pr. & vb. n. 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.

Countersink

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.
  2. A drill or cutting tool for countersinking holes.