joint liability

Definition from Nolo’s Plain-English Law Dictionary

When two or more persons are both responsible for a debt, claim, or judgment. It can be important to the person making the claim, as well as to a person who is sued, who can demand that anyone with joint liability for the alleged debt or claim for damages be joined in (brought into) the lawsuit with them. Compare: several liability

Definition provided by Nolo’s Plain-English Law Dictionary.