—v. also koun"tur-sīn'), [key]
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.
to sign (a document that has been signed by someone else), esp. in confirmation or authentication.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.