1. (

• alum ,
• ammonia_alum ,
• ammonium_alum

) a white crystalline double sulfate of aluminum: the ammonium double sulfate of aluminum ;

2. (

• alum ,
• potassium_alum ,
• potash_alum

) a white crystalline double sulfate of aluminum: the potassium double sulfate of aluminum ;

3. (

• alumnus ,
• alumna ,
• alum ,
• graduate ,
• grad

) a person who has received a degree from a school (high school or college or university) ;

4. (

• alum

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