Source : Webster's Revised Unabridged Dictionary (1913)

Galactose \Ga*lac"tose\, n. (Chem.)
   A white, crystalline sugar, {C6H12O6}, isomeric with
   dextrose, obtained by the decomposition of milk sugar, and
   also from certain gums. When oxidized it forms mucic acid.
   Called also {lactose} (though it is not lactose proper).

Source : WordNet®

galactose
     n : a simple sugar found in lactose [syn: {brain sugar}]