Definition from Wiktionary, the free dictionary
countersink (plural countersinks)
- a cylindrical recess, typically machined around a hole to admit a screw so that it sits flush with a surface.
a conical recess machined around a hole
- (transitive) To create such a conical recess.
- to countersink a hole for a screw
- (transitive) To cause to sink even with or below the surface.
- to countersink a screw or bolt into woodwork