资料来源 : Webster's Revised Unabridged Dictionary (1913)

Synallagmatic \Syn`al*lag*mat"ic\, a. [Gr. ?, from ? a mutual
   agreement, contract, fr. ? to exchange, negotiate with; sy`n
   with + ? to change.] (Law)
   Imposing reciprocal obligations upon the parties; as, a
   synallagmatic contract. --Bouvier.