From Sajun.org

A Speakeasy was an establishment that was used for selling and drinking of alcoholic beverages during the period of U.S. history known as Prohibition, when selling or buying alcohol was illegal.

Speakeasies became more popular and numerous as the Prohibition years progressed, as well as more commonly operated by those with connections to organized crime. While police and United States Federal Government agents would raid such establishments and arrest the owners and patrons, the business of running speakeasies was so lucrative that such establishments continued to flourish throughout the nation. In major cities, speakeasies could often be elaborate, offering food, live bands, and floor shows. Police were notoriously bribed by speakeasy operators to either leave them alone or at least give them advance notice of any planned raid.

Other slang terms for a speakeasy included "Blind pig", or, "Blind pigs".

Some discreet venues called smoke-easies have popped up in states such as New York, California, and Massachusetts where smoking in bars and clubs is prohibited.