verb (used with object), coun·ter·sank, coun·ter·sunk, coun·ter·sink·ing.
Examples from the Web for countersink
Bore all holes, where shown in the drawing, and countersink them.Toy Craft|Leon H. Baxter
Be sure to countersink the holes for the heads of the bolts.The Boy Mechanic, Book 2|Various
Two 1⁄4-inch holes were bored, as shown at d, in each piece, and countersunk with the countersink bit.Carpentry and Woodwork|Edwin W. Foster
Countersink for the heads on the back of the shield and so fasten the antlers in place.Home Taxidermy for Pleasure and Profit|Albert B. Farnham
The forms of the heads are as in Fig. 387, a being termed a Fillister, b a countersink, and c a round head.Modern Machine-Shop Practice, Volumes I and II|Joshua Rose