Definition - What does Co-Signer mean?
A co-signer is any person or entity who takes on financial responsibility for another person or entity’s financial obligation. In other words, a co-signer is promising to pay off the debt of the original signer in the case that the original signer ends up not paying his or her own debt.
Justipedia explains Co-Signer
Co-signers are usually necessary when an original signer has low or no credit history. For example, if a person has a history of not paying off his or her debt, then a car dealership may not sell a car to this person unless he or she has another person c-sign for the car that has good credit history. Also, an apartment complex may require a person just out of school to have a co-signer on their apartment because they currently have little or no credit history.