What does countersign mean?
A countersign is a second signature added to a document that has already been signed once, serving to confirm, validate, or authorize what the first signer has written. The practice appears wherever institutions require dual approval: bank cheques above a certain value, official applications such as passports and visas, contracts, treaties, and diplomatic instruments all commonly call for a countersignature before they take effect. The word also functions as a verb — to countersign a document is simply to add that confirming signature. In older military usage, a countersign was additionally a secret word exchanged between sentries and those seeking passage, paired with a daily password as a test of identity. Derived from Italian via Latin roots meaning 'against' and 'mark', the term carries a formal, procedural connotation and signals institutional oversight rather than personal initiative. It remains essential vocabulary in law, finance, and administration.
A second signature added to an already signed document to confirm or authorize it; formerly, also the secret word given in reply to a password by a sentry.
"The treaty takes effect only upon the countersign of both heads of state."
To add one's own signature to a document already signed by another person in order to confirm or validate it.
"You will need a doctor to countersign this medical certificate."
Transitive; the object is normally the document being validated.
Standard plural, used chiefly when referring to multiple validating signatures or, historically, multiple passwords.
"The file contained the signatures and countersigns of every approving officer."
In old military camps, the day's password had a partner called the countersign — get either one wrong at the sentry's post and you were in serious trouble.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of countersign
Countersign entered English in the late sixteenth or early seventeenth century, borrowed from Italian 'controsegno', formed from Latin 'contra' ('against' or 'opposite') and 'signum' ('sign' or 'mark'). It originally denoted the military password given in answer to a challenge before extending to the sense of a confirming signature. It shares its root with words such as signal, signature, resign, and signify, all descended from the Latin signum.
Related word forms
How countersign is actually used
Formal to neutral in register; most common in administrative, legal, banking, and diplomatic contexts where dual authorization is required. The verb is transitive and typically takes the document as its direct object.
Easily confused with countersign
To cosign is to sign jointly with another party, typically sharing legal responsibility as on a loan, whereas to countersign is to add a confirming signature to a document already signed by someone else.
Counterfeit means made in imitation with intent to deceive, while countersign refers to a legitimate secondary or confirming signature.