transitive verb. To sign (a previously signed document) to vouch for the authenticity of the document.

noun. A second or confirming signature on a previously signed document.

noun. undefined

noun. A sign or signal to be given to a sentry in order to obtain passage; a password.

noun. A secret sign or signal given in answer to another.

To sign opposite to another signature; sign additionally; superadd one's signature to by way of authentication, attestation, or confirmation: as, charters signed by a king are countersigned by a secretary.

Figuratively, to attest in any way; confirm; corroborate.

noun. A private signal, in the form of a word, phrase, or number, given to soldiers on guard, with orders to let no one pass unless he first gives that sign; a military watchword.

noun. The signature of a secretary or other subordinate officer to a writing signed by the principal or superior, to attest its authenticity; a counter-signature.

adjective. The signature of a secretary or other officer to a writing signed by a principal or superior, to attest its authenticity.

adjective. A private signal, word, or phrase, which must be given in order to pass a sentry; a watchword.

transitive verb. 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.

noun. a second signature added to a document to affirm the validity of the signature of the first person

verb. to add a second signature to a document, affirming the validity of the signature of another person

verb. add one's signature to after another's to attest authenticity

noun. a secret word or phrase known only to a restricted group

noun. a second confirming signature endorsing a document already signed

"Upon their approach to the bridge, the challenge, and interchange of sign and countersign, which is usual on such occasions, took place in due form; and as Rudolph’s party filed off one after another into the castle, he commanded them to wake their companions, with whom he intended to renew the patrol, and at the same time to send a relief to Arthur Philipson, whose watch on the bridge was now ended."