a sac under the skin at the base of the spine located in the opening between the buttocks muscles

a special case and almost always requires medical treatment including drainage and packing (putting gauze in the open abscess to assure it continues to drain)

a special kind of abscess that occurs in the crease of the buttocks

A special kind of abscess that occurs in the cleft between the buttocks. Forms frequently in adolescence after long trips that involve sitting. The word "pilonidal" is derived from the Latin words pilus (meaning hair) and nidus (meaning nest).

a nidi that is buried deep enough that there is no communication to the surface----SO it forms a cyst of the secretions

a pussy hair filled boil on the tailbone

A pilonidal cyst (from Latin meaning 'hair nest') is a blanket term for any type of skin infection near the tailbone. These are normally quite painful, occur somewhat more often in men than in women, and normally happen in early adulthood. Although usually found near the tailbone, this painful condition can be found in several places, including the navel or the armpit.