v. , n. /kown"teuhr singk'/ ; v. also /kown'teuhr singk"/ , v. , countersank, countersunk, countersinking , n.
v.t.
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.
n.
3. a tool for countersinking a hole.
4. a countersunk hole.
[ 1810-20; COUNTER- + SINK ]