a double sulphate of aluminum and potassium that is used as an astringent (among other things)(noun.artifact)
source: wordnet30
A double sulphate formed of aluminium and some other element (esp. an alkali metal) or of aluminium. It has twenty-four molecules of water of crystallization.(noun)
source: webster1913
verb (v)
To steep in, or otherwise impregnate with, a solution of alum; to treat with alum.(verb)