Definitions from Wiktionary ( )

▸ noun:  An astringent salt, usually occurring in the form of pale crystals, much used in the dyeing and tanning trade and in certain medicines, and now understood to be a double sulphate of potassium and aluminium (K₂SO₄·Al₂(SO₄)₃·24H₂O).
▸ noun:  (inorganic chemistry) Any similar double sulphate in which either or both of the potassium and aluminium is wholly or partly replaced by other univalent or tervalent cations.
▸ verb:  (transitive) To steep in, or otherwise impregnate with, a solution of alum; to treat with alum.
▸ noun:  (shortening, Canada, US) A past attendee or graduate (of any gender) of a college, university or other educational institution.

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