A blind boil

from The Collaborative International Dictionary of English v.0.48

Boil \Boil\, n. [Influenced by boil, v. See {Beal}, {Bile}.]
   A hard, painful, inflamed tumor, which, on suppuration,
   discharges pus, mixed with blood, and discloses a small
   fibrous mass of dead tissue, called the core.
   [1913 Webster]

   {A blind boil}, one that suppurates imperfectly, or fails to
      come to a head.

   {Delhi boil} (Med.), a peculiar affection of the skin,
      probably parasitic in origin, prevailing in India (as
      among the British troops) and especially at Delhi.
      [1913 Webster]