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Noun: alum  a-lum
  1. A white crystalline double sulphate of aluminium: the ammonium double sulphate of aluminium
    - ammonia alum, ammonium alum
     
  2. A white crystalline double sulphate of aluminium: the potassium double sulphate of aluminium
    - potassium alum, potash alum
     
  3. A person who has received a degree from a school (high school, college or university)
    - alumnus, alumna, graduate, grad
     
  4. A double sulphate of aluminium and potassium that is used as an astringent (among other things)

Derived forms: alums

Type of: Al, aluminium [Brit, Cdn], aluminum [N. Amer], astringent, astringent drug, atomic number 13, bookman, double salt, scholar, scholarly person, student, styptic

Encyclopedia: Alum