A person who signs a legal document as a joint guarantor or co-signer, sharing equal responsibility with another person for fulfilling a debt or obligation.
From Latin 'co-' (together) + 'pro-' (before) + 'mittere' (to send/promise). The legal term mirrors 'promisor' but indicates two parties equally bound by the same promise or obligation.
When your parent co-signs your student loan, they become a copromisor—and if you don't pay, they're equally on the hook legally. Banks love copromisors because it doubles their chances of getting paid back.
Legal term '-misor' derives from 'promissor.' Historical legal systems excluded women from property, contracts, and financial instruments, making 'promisor' implicitly male in early usage, though modern legal language is gender-neutral.
Use as-is in modern contexts. Legal terminology is now gender-neutral by standard practice.
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