What is the definition or description of: lactose intolerance?

Lactose intolerance: Lactose is a type of sugar found in milk and other dairy products. Lactose intolerance develops when the small intestine does not make enough of an enzyme called lactase. The body needs this enzyme to digest lactose. This is not a milk allergy, but instead an intolerance with gastrointestinal symptoms of crampy abdominal pain, gassiness and diarrhea worse with increasing amounts of dairy ingestion.