Noun alum has 4 senses
- alum, ammonia alum, ammonium alum - a white crystalline double sulfate of aluminum: the ammonium double sulfate of aluminum
--1 is a kind of aluminum, aluminium, Al, atomic number 13; double salt
- alum, potassium alum, potash alum - a white crystalline double sulfate of aluminum: the potassium double sulfate of aluminum
--2 is a kind of aluminum, aluminium, Al, atomic number 13; double salt
- alumnus, alumna, alum, graduate, grad - a person who has received a degree from a school (high school or college or university)
--3 is a kind of scholar, scholarly person, student
--3 has particulars: Ivy Leaguer; old boy
- alum - a double sulphate of aluminum and potassium that is used as an astringent (among other things)
--4 is a kind of astringent, astringent drug, styptic
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