This is the condition we all think we have. All it means, however, is the inability to digest molecules of lactose. It could be caused by the natural decline of production of the lactose-digesting enzyme lactase, or by reduced lactase activity caused by damage to the intestines, or by other intestinal ailments or medications that prevent the intestines from working properly. The term is a formal medical term that should properly be used only as a medical diagnosis following testing that proves that the condition exists. You'll notice that nothing is said in this definition about having any symptoms from this inability to digest lactose.
Many people test as being lactose maldigesters, but never show any symptoms.
Milk Intolerance due to Lactose Nitpickers may sometimes use this term to refer to symptoms experienced after eating or drinking milk or dairy products in food. Odd as it may seem, they may be no relationship at all between symptoms and low lactase levels in any given person. As you may expect from that definition, this term gets used pretty loosely to mean either lactose maldigestion or lactose intolerance or both. Hypolactasia Technically, a very low state of lactase activity in the small intestine. In practice, this is the European term that is the equivalent to lactase deficiency, used to mean either lactose maldigestion or lactose intolerance or both.