Legal Definition of Co-Signer: Someone who signs a document along with another person or persons, often assuming obligations to be shared with the other signers | Understanding the Legal Definition of a Co-Signer: Get a clear understanding of what it means to be a co-signer and how it can benefit business owners. Discover practical examples and the importance of having a co-signer in various legal and financial transactions. Approach co-signing with caution and make informed decisions with confidence