Date: 1400-1500 Language: French Origin: Latin laesio, from laedere 'to injure' lesion noun Related topics: Illness and Disabilityle???sion [countable] technicalMI damage to someone's skin or part of their body such as their stomach or brain, caused by injury or illness: acute gastric lesions Definition from the Longman Dictionary of Contemporary English Advanced Learner's Dictionary.