Pronunciation: ( —n., v.koun'tur-sīn"; —v. also koun"tur-sīn'),[key] —n. 1. a sign used in reply to another sign.
2. Mil.a secret sign that must be given by authorized persons seeking admission through a guarded area.
3. a signature added to another signature, esp. for authentication.
—v.t. to sign (a document that has been signed by someone else), esp. in confirmation or authentication.