A second signature added to a document to affirm the validity of the signature of the first person.
The response to a sign or signal.
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.
To make invalid. Especially applied to contract law.
To make or declare (an argument, statement, or theory) unsound or erroneous; disprove.
To render invalid; discredit.