Lac″tose′ (?), n. 1. (Physiol. Chem.) Sugar of milk or milk sugar; a crystalline sugar present in milk, and separable from the whey by evaporation and crystallization. It has a slightly sweet taste, is dextrorotary, and is much less soluble in water than either cane sugar or glucose. Formerly called lactin.
2. (Chem.) See Galactose.