\Blain\ (bl[=a]n), n. [OE. blein, bleyn, AS. bl[=e]gen;
akin to Dan. blegn, D. blein; perh. fr. the same root as E.
bladder. See {Bladder}.]
1. An inflammatory swelling or sore; a bulla, pustule, or
   blister.

         Blotches and blains must all his flesh emboss.
                                               --Milton.

2. (Far.) A bladder growing on the root of the tongue of a
   horse, against the windpipe, and stopping the breath.