alum
     n 1: a white crystalline double sulfate of aluminum: the ammonium
          double sulfate of aluminum [syn: {ammonia alum}, {ammonium
          alum}]
     2: a white crystalline double sulfate of aluminum: the
        potassium double sulfate of aluminum [syn: {potassium alum},
         {potash alum}]
     3: a person who has received a degree from a school (high
        school or college or university) [syn: {alumnus}, {alumna},
         {graduate}, {grad}]
     4: a double sulphate of aluminum and potassium that is used as
        an astringent (among other things)
Source: WordNet® 2.0