BLISTER, a small vesicle filled with serous fluid raised on the skin by a burn, by rubbing on a hard surface, as on the hand in rowing, or by other injury ; also used of a similar condition caused artificially, by the application of mustard, of various kinds of fly (see CANTHARIDES) and of other vesicatories. Similar small swellings, filled with fluid or air, on plants and on the surface of steel or paint, etc., are also called "blisters."