[koun-ter-bawr, -bohr; koun-ter-bawr, -bohr] 
noun, verb, -bored, -bor⋅ing.| 1. | a tool for enlarging a drilled hole for a portion of its length, as to permit sinking a screw head. |
| 2. | the portion of the hole so enlarged. |
| 3. | to enlarge (a drilled hole) along part of the length of the hole by drilling with a bit having a greater diameter. |
tərˌbɔr