lesion (lee-zh<<schwa>>n).1. An injury or wound; esp., an area of wounded tissue. 2.Civil law. Loss from another’s failure to perform a contract; the injury suffered by one who did not receive the equivalent value of what was bargained for. La. Civ. Code art. 2589. — Also spelled (in sense 2) lésion. [Cases: Vendor and Purchaser  89. C.J.S. Vendor and Purchaser §§ 182, 184–185.] 3.LAESIO ENORMIS.

“The concept of lésion, unknown as such to the common law, may be defined as a detriment to one of the parties to a contract which results from an imbalance or disparity between the performance promised on the two sides. Down through the ages, civilians have differed over whether it gave the injured party a right of avoidance or rescission. Classical Roman law, designed for a society whose members were strong enough to protect their own interests, denied the right, but by the time of the French Revolution the right had come to be recognized, particularly by the canonists and Pothier. But the Revolution, both because of its emphasis on individual will and because of economic reasons, was hostile to the concept of lésion and the Civil Code provided that it did not affect the validity of a contract except in certain prescribed instances, most notably the case of the vendor of real property. The number of exceptions was enlarged both by subsequent legislation and, at least indirectly, by judicial decision, and this raised a question of the reversal of the general principle that rejected the concept.” Allan Farnsworth, “The Development of the Civil Law of Obligations in New States: Senegal, Madagascar, and Ethiopia,” in Essays on the Civil Law of Obligations 64 (Joseph Dainow ed., 1969).

[Blacks Law 8th]