noun.
A skin swelling or sore; a blister; a blotch.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
noun.
an inflammatory swelling or sore
Word Usage
"The blain is a vesicular enlargement on the lateral and under part of the tongue in horses, oxen, and dogs, which, although not of unfrequent occurrence, or peculiarly fatal result, has not been sufficiently noticed by veterinary authors."