'alum' definitions:

A white crystalline double sulfate of aluminum: the ammonium double sulfate of aluminum [syn: alum, ammonia alum, ammonium alum]

A white crystalline double sulfate of aluminum: the potassium double sulfate of aluminum [syn: alum, potassium alum, potash alum]

A person who has received a degree from a school (high school or college or university) [syn: alumnus, alumna, alum, graduate, grad]

A double sulphate of aluminum and potassium that is used as an astringent (among other things)