Definify.com
Webster 1913 Edition
Counterbore
Coun′ter-boreˊ
(-b?rˊ)
, Noun.
1.
A flat-bottomed cylindrical enlargement of the mouth of a hole, usually of slight depth, as for receiving a cylindrical screw head.
2.
A kind of pin drill with the cutting edge or edges normal to the axis; – used for enlarging a hole, or for forming a flat-bottomed recess at its mouth.
Counˊter-bore′
(kounˊt?r-b?r′)
, Verb.
T.
To form a counterbore in, by boring, turning, or drilling; to enlarge, as a hole, by means of a counterbore.