countersink

American  

[koun-ter-singk, koun-ter-singk] / ˈkaʊn tərˌsɪŋk, ˌkaʊn tərˈsɪŋk /

verb (used with object)

countersank, countersunk, countersinking

1. to enlarge the upper part of (a cavity), especially by chamfering, to receive the cone-shaped head of a screw, bolt, etc.

2. to cause (the head of a screw, bolt, etc.) to sink into a prepared depression so as to be flush with or below the surface.

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noun

1. a tool for countersinking a hole.

2. a countersunk hole.

countersink British  

/ ˈkaʊntəˌsɪŋk /

verb

1. to enlarge the upper part of (a hole) in timber, metal, etc, so that the head of a bolt or screw can be sunk below the surface

2. to drive (a screw) or sink (a bolt) into such an enlarged hole

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noun

1. Also called: countersink bit.  a tool for countersinking

2. a countersunk depression or hole

Etymology

Origin of countersink

First recorded in 1810–20; counter- + sink

Example Sentences

With its radula, a rasp of seven rows of teeth, the moon snail countersinks its unmistakable signature: a perfect round hole, right at the clam’s hinge, to pop open its meal.

From Seattle Times

It is secured to the skull with screws placed in 2 mm countersunk holes.

From New York Times

The chocks in which these boats rest are provided with gunmetal wheels, which run in transverse gunmetal tracks, countersunk on the deck.

From Scientific American

Instead of the hole being countersunk, however, it may be cupped or counterbored, as in Fig.

From Project Gutenberg

A bolt with a countersunk head is shown in fig.

From Project Gutenberg