p. p. & a. from Countersink. 1. Chamfered at the top; -- said of a hole. [ 1913 Webster ]
2. Sunk into a chamfer; as, a countersunk bolt. [ 1913 Webster ]
3. Beveled on the lower side, so as to fit a chamfered countersink; as, a countersunk nailhead. [ 1913 Webster ]