From Longman Dictionary of Contemporary Englishcountersigncoun‧ter‧sign /ˈkaʊntəsaɪn $ -ər-/ verb [transitive] SIGN YOUR NAMEto sign a paper that has already been signed by someone else The note must be countersigned by a doctor.→ See Verb table
Examples from the Corpus
countersign• Each cheque had to be signed and countersigned.• So the company introduced the travellers cheque, which had no value until it was countersigned.• We are specifically considering the proposal that the donor card should be countersigned.• The cheques had not been countersigned, and it was arguable that the bank had no authority to honour them.• The form contemplated that it would also be countersigned by an obstetrician, but it was not so signed.• You have to get your visa countersigned by someone at the embassy.• All cheques shall be signed and countersigned by such persons as the Executive Committee shall determine.• I'm supposed to countersign this check in their presence.• Route Seventeen Account holders do not require an adult to countersign when opening an account or on any of their transactions.From Longman Business Dictionarycountersigncoun‧ter‧sign /ˈkaʊntəsaɪn-ər-/ verb [transitive] to sign a document that someone else has signed, for example to show your agreementThe cheques had not been countersigned, and the bank had no authority to honour them.→ See Verb table 