A good where a rise in price actually leads to an increase in demand.
Below is a diagram to illustrate the good's demand curve. In this instance the curve has a positive slope and therefore is upward sloping due to the positive relationship between the two variables: price and quantity demanded. It is extremely rare for a good to have this positive relationship between price and quantity demanded and in most cases is just an empirical theory rather than a form of relatiy. But on example of a giffen good in the real world is basic food stapes in times of economic crises. The idea is that if an individual/family is struggiling financially and the price of the basic food essentials increase, these individuals end up purchasing more of this essential food item as they can't afford more expensive food items in its place despite the price of the essential good.