counterbore

transitive verb
coun·​ter·​bore | \ ¦kau̇ntə(r)+\

Definition of counterbore

 (Entry 1 of 2)

: to form a counterbore in : enlarge (part of a hole) by means of a counterbore

counterbore

noun

Definition of counterbore (Entry 2 of 2)

1 : a flat-bottomed enlargement of the mouth of a cylindrical bore
2 : a drill for making a counterbore — compare countersink

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History and Etymology for counterbore

Transitive verb

counter- + bore

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