2  definitions  found 
 
  From  Webster's  Revised  Unabridged  Dictionary  (1913)  [web1913]: 
 
  Alumina  \A*lu"mi*na\,  n.  [L.  alumen,  aluminis  See  {Alum}.] 
  (Chem.) 
  One  of  the  earths,  consisting  of  two  parts  of  aluminium  and 
  three  of  oxygen,  {Al2O3}. 
 
  Note:  It  is  the  oxide  of  the  metal  aluminium,  the  base  of 
  aluminous  salts,  a  constituent  of  a  large  part  of  the 
  earthy  siliceous  minerals,  as  the  feldspars,  micas, 
  scapolites  etc.,  and  the  characterizing  ingredient  of 
  common  clay,  in  which  it  exists  as  an  impure  silicate 
  with  water,  resulting  from  the  decomposition  of  other 
  aluminous  minerals.  In  its  natural  state,  it  is  the 
  mineral  corundum. 
 
  From  WordNet  r  1.6  [wn]: 
 
  alumina 
  n  :  any  of  various  forms  of  aluminum  oxide  occurring  naturally 
  as  corundum  [syn:  {aluminum  oxide},  {aluminium  oxide}] 

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