—v. also koun"tur-singk'), [key]
—v., -sank, -sunk, -sink•ing,
1. to enlarge the upper part of (a cavity), esp. 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.
1. a tool for countersinking a hole.
2. a countersunk hole.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.