- al|um1 «AL uhm», noun.1. a whitish mineral salt used in medicine and in dyeing; potash alum. A pencil of alum is sometimes used to stop the bleeding of a small cut. Formula: KAI(SO4)2•12H2O2. a colorless, crystalline salt containing ammonia, used in baking powder, foam fire extinguishers, the purification of drinking water, and in medicine; ammonia alum. Formula: NH4Al(SO4)2•12H2O3. any one of a group of double salts analogous to and including potash alum, formed by the union of the sulfate of a trivalent metal, such as aluminum, chromium, or iron, with the sulfate of a monovalent alkali metal or ammonium.4. U.S. = aluminum sulfate. (Cf. ↑aluminum sulfate)╂[< Old French alum < Latin alūmen]al|um2 «AL uhm», noun.a graduate or former student of a particular school: »
The theater was filled with Shakespeare Academy alums.╂[ shortening of alumnus]
Useful english dictionary. 2012.