/v., n. ˈkaʊntərˌsɪŋk;v. also ˌkaʊntərˈsɪŋk/Show Spelled[v., n. koun-ter-singk;v. also -koun-ter-singk]Show IPAverb, coun·ter·sank, coun·ter·sunk, coun·ter·sink·ing,noun
verb (used with object)
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.