|pīlə|nīd ə l adjective
Etymology: pil- (I) + Latin nidus nest + English -al — more at nest
1. : containing hair nested in a cyst — used of congenitally anomalous cysts in the sacrococcygeal area that often become infected and discharge through a channel near the anus
2. : of, relating to, involving, or for use on pilonidal cysts, tracts, or sinuses