[koun-ter-bawr, -bohr; koun-ter-bawr, -bohr]
a tool for enlarging a drilled hole for a portion of its length, as to permit sinking a screw head.
the portion of the hole so enlarged.
verb (used with object), coun·ter·bored, coun·ter·bor·ing.
to enlarge (a drilled hole) along part of the length of the hole by drilling with a bit having a greater diameter.
Origin of counterbore
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for counterboring
Historical Examples of counterboring
The counterboring was then accomplished in the manner shown in Fig. 2515.
For counterboring small holes or for facing the metal around their ends, the form of counterbore shown in Fig. 1746 is employed.