Definition of countersink
verb (past and past participle countersunk)
[with object] enlarge and bevel the rim of (a drilled hole) so that a screw, nail, or bolt can be inserted flush with the surface: drill and countersink the hole for mounting the ladder to the wall drive (a screw, nail, or bolt) into a countersunk hole: (as adjective countersunk)countersunk screw heads
