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

(transitive) To create such a conical recess. / (transitive) To cause to sink even with or below the surface.

A spy working in counterintelligence.

(intransitive) To carry out counterespionage.

(law) A second signature added to a document to affirm the validity of the signature of the first person. / The response to a sign or signal.

(transitive) To sign on the opposite side of (a document). / (transitive, by extension) To add a second signature to a document, affirming the validity of the signature of another person.

simple past tense of countersink

(architecture) The outer slope of a defensive or fortified ditch

plural of counterscarp

simple past tense and past participle of countersing