bilateral contract

from WordNet (r) 3.0 (2006)

bilateral contract
    n 1: a contract involving mutual promises (each party is both
         promisor and promisee)

from Bouvier's Law Dictionary, Revised 6th Ed (1856)

BILATERAL CONTRACT, civil law. A contract in which both the contracting 
parties are bound to fulfill obligations reciprocally towards each other; 
Lec. Elem. Sec. 781; as a contract of sale, where one becomes bound to 
deliver the, thing sold, and the other to pay the price of it. Vide 
Contract; Synallagmatic contract.