[coun.ter.sink] vt -sunk ; -sink.ing (1816) 1: to make a countersink on
2: to set the head of (as a screw) at or below the surface
[2]countersink n (1816) 1: a bit or drill for making a funnel-shaped enlargement at the outer end of a drilled hole
2: the enlargement made by a countersink