countersign

/ˌkaʊntərˈsaɪn/

Other forms: countersigned; countersigns; countersigning

Definitions of countersign

1. verb

   add one's signature to after another's to attest authenticity
   “You must countersign on this line of the contract”

   type of:

   sign

   be engaged by a written agreement
2. noun

   a second confirming signature endorsing a document already signed
   synonyms: countersignature

   type of:

   signature

   your name written in your own handwriting
3. noun

   a secret word or phrase known only to a restricted group
   synonyms: parole, password, watchword, word

   type of:

   arcanum, secret

   information known only to a special group

   positive identification

   evidence proving that you are who you say you are; evidence establishing that you are among the group of people already known to the system; recognition by the system leads to acceptance