Price elasticity of demand is a relationship between the changes in prices charged for a good or service (here taken as Hotel rooms) and the change in the amount demanded.
Other definition:
Price elasticity of demand is a measure of the variability that can be expected in sales when prices are changed. Unity elasticity would see equal increase in sales to in reaction to a decrease in price. Inelastic demand would not change when prices went down or up.
The Travel-Glossary: Everything about Travelling, Sightseeing and the World.