A masquerade, in the seventeenth and eighteenth centuries, was a masked ball, where participants would wear masks, and often adopt elaborate costumes. Masquerades adopted some of the characteristics of carnival, but were organised as commercial undertakings. Like carnival, they came to be associated with licence and moral depravity and died out in the new moral seriousness that began to appear in Western society in the late eighteenth century.
In modern parlance a masquerade is a sham: a performance - often associated with politics - put on to deceive the observer.