The response to a sign or signal.
A second signature added to a document to affirm the validity of the signature of the first person.
To sign on the opposite side of (a document).
To add a second signature to a document, affirming the validity of the signature of another person.
A word relayed to a person to gain admittance to a place or to gain access to information.
A string of characters used to log in to a computer or network, to access a level in a video game, and so on; archetypally a word but nowadays often an alphanumeric string or a phrase.
To protect with a password.