countersink

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

verb (used with object), coun·ter·sank, coun·ter·sunk, coun·ter·sink·ing.

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

noun

a tool for countersinking a hole.
a countersunk hole.

Origin of countersink

First recorded in 1810–20; counter- + sink

Words nearby countersink

countershading, countershaft, countershock, countersign, countersignature, countersink, counterspy, counterstain, counterstamp, counterstatement, counterstroke

British Dictionary definitions for counter-sinking

countersink
/ (ˈkaʊntəˌsɪŋk) /

verb -sinks, -sinking, -sank or -sunk (tr)

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

noun

Also called: countersink bit a tool for countersinking
a countersunk depression or hole