Definition of "countersink" []

• A hole with the top part enlarged so that the head of a screw or bolt will lie flush with or below the surface. (noun)
• A tool for making such a hole. (noun)
• To make a countersink on or in. (verb-transitive)
• To drive (a screw or bolt) into a countersink. (verb-transitive)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Drills are to be procured from the various dealers, but can be made from steel wire softened in the fire and filed to a sharp three-cornered point -- afterwards tempered to hardness -- for the smaller eggs, or filed up for the larger eggs to the pattern of a "countersink" used for wood; indeed, the smallest-sized"
• "Alternatively, they can be retrofitted to devices such as countersink gauges, measuring situations where conventional 1: 1-ratio indicators would be rendered useless."
• ""countersink" made -- to be procured at any ironmonger's -- will do very well for eggs the size of a hen's."