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synallagmatic contracta bilateral contract creating reciprocal obligations. Sale is an example.
Collins Dictionary of Law © W.J. Stewart, 2006
SYNALLAGMATIC CONTRACT, civil law. A synallagmatic or bilateral contract is one by which each of the contracting parties binds himself to the other; such are the contracts of sale, hiring, &c. Poth. Ob. n. 9. Vide Contract.
A Law Dictionary, Adapted to the Constitution and Laws of the United States. By John Bouvier. Published 1856.