The term 'under-signs' generally refers to a person who signs or acknowledges a document, agreement or contract. Some of the synonyms for this term include 'undersign,' 'subscribes,' 'authenticates,' 'endorses,' 'ratifies' and 'approves.' These words essentially convey the act of signing something as a binding agreement or validation. Other similar phrases that can be used to convey the meaning of 'under-signs' include 'puts one's signature to,' 'affirms,' 'attests,' 'certifies' and 'confirms.' Regardless of the word or phrase used, the underlying idea is that an individual is providing their signature or approval to a document or agreement.