An exceptional demand curve is:

In some exceptional cases law of demand is violated. For example in the case of giffen goods, as the price of giffen goods rise then there demand will also rise. And in the case of commodities which are used as a status symbols (also known as Veblen goods), as the price of these goods rise then their demand will also rise. So in above exceptional cases, the demand curve will upward sloping from left to right like supply curve showing positive relationship between quantity demanded and price. This demand curve is also called exceptional demand curve}