Webster's English Dictionary

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lesion

le.sion \'le--zh*n\ n [ME, fr. MF, fr. L laesion-, laesio, fr. laesus, pp. 
   of la]edere to injure 1: INJURY, HARM  2: an abnormal change in structure 
   of an organ or part due to injury or dis ease; esp : one that is 
   circumscribed and well defined