noun

• (by extension) A permanent negative effect on someone's mind, caused by a traumatic experience.
  "Thus, it is wise to avoid cultivating an emotional scar, as it can play havoc with your happiness and success."

verb

• (transitive) To mark the skin permanently.
  "Yet I'll not shed her blood; / Nor scar that whiter skin of hers than snow."
• (intransitive) To form a scar.
  "Iron and coal were the magnets that drew railways to this land of lovely valleys and silent mountains—for such it was a century-and-a-half ago, before man blackened the valleys with the smoke of his forges, scarred the green hills with his shafts and waste-heaps, and drove the salmon from the quiet Rhondda and the murmuring Taff."
• (transitive, figurative) To affect deeply in a traumatic manner.
  "Seeing his parents die in a car crash scarred him for life."