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1. A secret word or phrase known only to a restricted group
   "he forgot the countersign";
   - password, watchword, word, parole
    
2. A second confirming signature endorsing a document already signed
   - countersignature

1. Add one's signature to after another's to attest authenticity
   "You must countersign on this line of the contract"

Derived forms: countersigned, countersigning, countersigns

Type of: arcanum, positive identification, secret, sign, signature

Encyclopedia: Countersign