A contract, the parties to which enter into mutual engagements. A mutual or bilateral contract. civil law. One in which the parties enter into mutual engagements. 2. They are divided into perfect and imperfect. When they are perfectly reciprocal, the obligation of each of the parties is equally a principal part of the contract, such as sale, partnership Contracts imperfectly reciprocal are those in which the obligation of one of the parties only is a principal obligation of the contract; as, mandate, deposit, loan for use, and the like. In all reciprocal contracts the consent of the parties must be expressed.