co·sign·er 
/ˈkoʊˌsaɪnɚ/ noun
plural co·sign·ers /ˈkoʊˌsaɪnɚ/ noun [count] : a person who signs an official document (such as a loan, contract, or law) with another person
▪ Both senators are cosigners of the bill. : a person who cosigns something ▪ My mother agreed to be a cosigner on my car loan.
▪ Both senators are cosigners of the bill. : a person who cosigns something ▪ My mother agreed to be a cosigner on my car loan.
