What does "countersink" mean?

A conical recess, typically machined at the mouth of a hole to admit a screw (with a matching taper) so that the screw sits flush with a surface.

What is a synonym for "countersink"?

Common synonyms include: bite, bore, broach, counterbore, counterbore, countersink bit.

noun, verb

noun, verb ·Uncommon ·College level

Noun

1
A conical recess, typically machined at the mouth of a hole to admit a screw (with a matching taper) so that the screw sits flush with a surface.
2
a bit for enlarging the upper part of a hole wordnet
3
The cutter used to cut such a recess. (Also used, at less depth, for edge-breaking/deburring.)
"Holonym: center drill (combined drill and countersink)"
4
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 wordnet

Verb

1
To create such a conical recess. transitive
"to countersink a hole for a screw"
2
insert (a nail or screw below the surface, as into a countersink) wordnet
3
To cause to sink even with or below the surface. ambitransitive
"to countersink a screw or bolt into woodwork"

"Holonym: center drill (combined drill and countersink)"

From counter- + sink.

Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.