Final answer:
A black market is an illegal market in which the equilibrium price exceeds the price ceiling. It arises when sellers and buyers engage in transactions outside the legal market to bypass the price restriction.
Step-by-step explanation:
An illegal market in which the equilibrium price exceeds the price ceiling is referred to as a black market. This occurs when a price ceiling, which is a legally fixed maximum price, is set below the equilibrium price determined by supply and demand. The black market arises as sellers and buyers engage in transactions outside the legal market to bypass the price restriction.