The seven dirty words are seven words that were prohibited from use on broadcast media in the United States, including both over-the-air television and radio stations. The original list of seven is:
Comedian George Carlin recorded a monologue that was called "Seven Words You Can Never Say on Television." The monologue was played on Pacifica radio station WBAI-FM. A man complained to the Federal Communications Commission (FCC) because his son had heard the broadcast.
The FCC asked Pacifica for a response, then issued a declaratory order upholding the complaint. No specific sanctions were included in the order, but WBAI was put on notice that "in the event subsequent complaints are received, the Commission will then decide whether it should utilize any of the available sanctions it has been granted by Congress."
Pacifica appealed the decision, which was overturned by the Court of Appeals. The FCC in turn appealed the case to the Supreme Court, which ruled in favor of the FCC, see: FCC v. Pacifica Foundation 438 U.S. 726 (1978).
This 1978 decision formally established indecency regulation in American broadcasting. In follow-up rulings, the FCC clarified that the words might be acceptable under certain circumstances, particularly at times when children would not be expected to be in the audience.
See also: Howard Stern, Communications Decency Act