countersink

From counter- +‎ sink.

countersink (plural countersinks)

1. a cylindrical recess, typically machined around a hole to admit a screw so that it sits flush with a surface.

countersink (third-person singular simple present countersinks, present participle countersinking, simple past countersank or countersunk, past participle countersunk)

1. (transitive) To create such a conical recess.

   to countersink a hole for a screw

2. (transitive, intransitive) To cause to sink even with or below the surface.

   to countersink a screw or bolt into woodwork

   • 2010, Larry Pardey, Details of Classic Boat Construction, pages 7-30:

     I countersank into the locust just enough to make the nailhead flush.

• counterbore
• sink
• spotface