Countersunk

Webster's Dictionary of the English Language

·p.p. & ·adj Chamfered at the top;

— said of a hole.

II. Countersunk ·Impf & ·p.p. of Countersink.

III. Countersunk ·p.p. & ·adj Sunk into a chamfer; as, a countersunk bolt.

IV. Countersunk ·p.p. & ·adj Beveled on the lower side, so as to fit a chamfered countersink; as, a countersunk nailhead.