Countersign Definition

To authenticate (a previously signed document) by adding one's own signature.

To sign one’s own name next to one’s own or someone else’s to authenticate, reinforce, or verify the first signature.

To sign on the opposite side of (an instrument or writing).

A signature added to a document previously signed by another, for authentication or confirmation.

A secret word or signal which must be given to a guard or sentry by someone wishing to pass; password.

A secret sign or signal in answer to another, as in a secret society.