A Veblen good is a good for which people's desire to buy the good increases with an increase in the price of the good, and decreases with a decrease in the price of the good. Thus, the demand for a Veblen good may increase with an increase in price. The effect is also sometimes called the Veblen effect.
Veblen goods are so named after Thorstein Veblen, who introduced the idea of conspicuous consumption: people consuming goods in order to display their income or wealth. Veblen goods are ostensibly an exception to the law of supply and demand.
Veblen goods are not to be confused with Giffen goods. Giffen goods are also goods for which the demand increases with an increase in price, but this is because of the substitution effect from a superior good, rather than due to an increased desire to consume the good.