noun

• (medicine) Something applied to the skin to raise a blister; a vesicatory or other applied medicine.
  "'T is written in the Hebrew Chronicle, / How the physicians, leaving pill and potion, / Prescribed, by way of blister, a young belle, / When old King David's blood grew dull in motion, / And that the medicine answered very well […]"
• (roofing) An enclosed pocket of air, which may be mixed with water or solvent vapor, trapped between impermeable layers of felt or between the membrane and substrate.
• (uncountable) A form of smelted copper with a blistered surface.

verb

• (transitive) To raise blisters on.
  "a chemical agent that blisters the skin"
• (cooking, transitive) To sear after blaching.
• (intransitive) To have a blister form.
  "A poorly formulated mortar mixture will result in plaster that blisters and cracks."
• (transitive) To criticise severely.