Source : Webster's Revised Unabridged Dictionary (1913)

Frankincense \Frank"in*cense\, n. [OF. franc free, pure + encens
   incense.]
   A fragrant, aromatic resin, or gum resin, burned as an
   incense in religious rites or for medicinal fumigation. The
   best kinds now come from East Indian trees, of the genus
   {Boswellia}; a commoner sort, from the Norway spruce ({Abies
   excelsa}) and other coniferous trees. The frankincense of the
   ancient Jews is still unidentified.

Source : WordNet®

frankincense
     n : an aromatic gum resin obtained from various Arabian or East
         African trees; formerly valued for worship and for
         embalming and fumigation [syn: {olibanum}, {gum olibanum},
          {thus}]