Source : Webster's Revised Unabridged Dictionary (1913)

Blister \Blis"ter\, n. [OE.; akin to OD. bluyster, fr. the same
   root as blast, bladder, blow. See {Blow} to eject wind.]
   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. --Dunglison.

   {Blister beetle}, a beetle used to raise blisters, esp. the
      {Lytta (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}.

Cantharis \Can"tha*ris\, n.; pl. {Cantharides}. [L., a kind of
   beetle, esp. the Spanish fly, Gr. kanqari`s.] (Zo["o]l.)
   A beetle ({Lytta, or Cantharis, vesicatoria}), havin1g an
   elongated cylindrical body of a brilliant green color, and a
   nauseous odor; the blister fly or blister beetle, of the
   apothecary; -- also called {Spanish fly}. Many other species
   of {Lytta}, used for the same purpose, take the same name.
   See {Blister beetle}, under {Blister}. The plural form in
   usually applied to the dried insects used in medicine.