Wiktionary
price floor
n. (context business English) An imposed lower limit on the price charged for a good or service.
WordNet
price floor
n. floor below which prices are not allowed to fall; "the government used price supports to maintain the price floor"
Wikipedia
Price floor
A price floor is a government- or group-imposed price control or limit on how low a price can be charged for a product. A price floor must be higher than the equilibrium price in order to be effective.