countersank See {countersink} countersink n 1: a hole (usually in wood) with the top part enlarged so that a screw or bolt will fit into it and lie below the surface 2: a bit for enlarging the upper part of a hole [syn: {counterbore}, {countersink bit}] v : insert (a nail or screw below the surface, as into a countersink) [syn: {set}] [also: {countersunk}, {countersank}]