any localized abnormal structural change in a bodily part
"The doctor diagnosed the patient's persistent headaches as being caused by a small lesion on the surface of his brain."
A wound or injury.
"The doctor examined his knee and identified a painful lesion caused by the fall."
To wound or injure, especially in an experiment or other controlled procedure.
"The researchers carefully applied a laser to create a precise lesion on the mouse's brain tissue for the study."