Definition from Wiktionary, the free dictionary
countersign (plural countersigns)
- 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.
- Only those who give the countersign may enter the Masonic Lodge.
- (transitive) To sign on the opposite side of (an instrument or writing).
- (transitive, by extension) to add a second signature to a document, affirming the validity of the signature of another person
add a second signature