coun•ter•bore
Pronunciation: (koun'tur-bôr", -bōr"&wdspckoun'tur-bôr', -bōr'), [key]
— n., v., -bored, -bor•ing.
—n.
- 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.
—v.t.
- to enlarge (a drilled hole) along part of the length of the hole by drilling with a bit having a greater diameter.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.