1. (law) a person who attests to the genuineness of a document or signature by adding their own signature
   "The lawyer served as an attestant for the contract signing";
   - witness, attestor, attestator [formal]
    
2. Someone who affirms or vouches for the correctness or truth or genuineness of something
   "The attestant signed the document, confirming its authenticity";
   - attester

Derived forms: attestants

Type of: informant, signatory, signer, witness, witnesser [rare]