Watchword
Part of speech: noun
Definition: a prearranged reply to the challenge of a sentry or a guard; a password or signal by which friends can be known from enemies a word used as a motto, as expressive of a principle or rule of action; a maxim, byword a rallying cry
Countersign
Part of speech: verb
Definition: to add a second signature to a document, affirming the validity of the signature of another person
Part of speech: noun
Definition: a second signature added to a document to affirm the validity of the signature of the first person