pilonidal

/ˌpaɪloʊˈnaɪdəl/
adjective
  1. Relating to a cyst or sinus that occurs near the tailbone, often containing hair and skin debris.
    • Surgery is sometimes needed to remove a pilonidal sinus that keeps getting infected.
    • Pilonidal disease is more common in young men who sit for long periods.
    • The doctor diagnosed him with a pilonidal cyst after he complained of pain at the base of his spine.