unilateral contract

A contract in which one party (the promisor) undertakes to do or refrain from doing something if the other party (the promisee) does or refrains from doing something, but the promisee does not undertake to do or refrain from doing that thing. An example of a unilateral contract is one in which the promisor offers a reward for the giving of information. See also *synallagmatic contract.