comaker
noun
co·mak·er (ˌ)kō-ˈmā-kər 
: one that participates in an agreement
specifically : one who stands to meet a financial obligation in the event of the maker's default
Word History
First Known Use
circa 1934, in the meaning defined above
Legal Definition
co-maker
noun
co-mak·er
ˈkō-ˌmā-kər
: one of two or more persons who sign an instrument to indicate a promise to pay a financial obligation
Note: Any co-maker may be sued for the entire amount of the indebtedness, although a co-maker who is forced to pay more than his or her share may seek contribution from the other co-makers.