Definitionen
1.NounAn 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). .mw-parser-output .defdate{font-size:smaller}
2.NounAny similar double sulphate in which either or both of the potassium and aluminium is wholly or partly replaced by other univalent or tervalent cations.
3.VerbTo steep in, or otherwise impregnate with, a solution of alum; to treat with alum.
4.NounA past attendee or graduate (of any gender) of a college, university or other educational institution.