To sign on the opposite side of (an instrument or writing); hence, to sign in addition to the signature of a principal or superior, in order to attest the authenticity of a writing.
- To sign (a previously signed document), as for authentication.
- A second or confirming signature, as on a previously signed document. Also called countersignature.
- A sign or signal to be given to a sentry in order to obtain passage; a password.
- A secret sign or signal given in answer to another.