The Collaborative International Dictionary of English v.0.48:

Lesion \Le"sion\ (l[=e]"zh[u^]n), n. [F. l['e]sion, L. laesio,
   fr. laedere, laesum, to hurt, injure.]
   A hurt; an injury. Specifically:
   (a) (Civil Law) Loss sustained from failure to fulfill a
       bargain or contract. --Burrill.
   (b) (Med.) Any morbid change in the exercise of functions or
       the texture of organs. --Dunglison.
       [1913 Webster]

WordNet (r) 3.0 (2006):

lesion
    n 1: any localized abnormal structural change in a bodily part
    2: an injury to living tissue (especially an injury involving a
       cut or break in the skin) [syn: wound, lesion]