Blis·ter n.
 1. A vesicle of the skin, containing watery matter or serum, whether occasioned by a burn or other injury, or by a vesicatory; a collection of serous fluid causing a bladderlike elevation of the cuticle.
    And painful blisters swelled my tender hands.   --Grainger.
 2. Any elevation made by the separation of the film or skin, as on plants; or by the swelling of the substance at the surface, as on steel.
 3. A vesicatory; a plaster of Spanish flies, or other matter, applied to raise a blister.
 Blister beetle, a beetle used to raise blisters, esp. the Lytta vesicatoria (or Cantharis vesicatoria), called Cantharis or Spanish fly by druggists. See Cantharis.
 Blister fly, a blister beetle.
 Blister plaster, a plaster designed to raise a blister; -- usually made of Spanish flies.
 Blister steel, crude steel formed from wrought iron by cementation; -- so called because of its blistered surface. Called also blistered steel.
 Blood blister. See under Blood.