1. countersunk - Adjective
2. countersunk - Verb
Derived from countersink
of Countersink
Chamfered at the top; -- said of a hole.
Sunk into a chamfer; as, a countersunk bolt.
Beveled on the lower side, so as to fit a chamfered countersink; as, a countersunk nailhead.
Source: Webster's dictionary