verb (used with object), coun·ter·sank, coun·ter·sunk, coun·ter·sink·ing.
Examples from the Web for countersunk
For this purpose a countersunk rammer head to fit over the head of the ball had to be used.The Development of Armor-piercing Shells|Carlos de Zafra
With a blunt-pointed knife make three countersunk holes in the edge of the mould.Taxidermy and Zoological Collecting|William T. Hornaday
Cast-iron tubes are constantly applied; they should have turned ends with wrought-iron collars and countersunk screws.
This projection drops into an opening in the bottom of the drawer, and engages a countersunk rod which is passed through the hole.
Round upper edges, and secure to frame by flat-head screws from the under side through holes bored and countersunk.Carpentry and Woodwork|Edwin W. Foster