I. |kau̇ntə(r)+ transitive verb
Etymology: counter- + bore
: to form a counterbore in : enlarge (part of a hole) by means of a counterbore
II. ˈ ̷ ̷ ̷ ̷+ˌ- noun
1. : a flat-bottomed enlargement of the mouth of a cylindrical bore
2. : a drill for making a counterbore — compare countersink