Pirate radio is illegal or unregulated radio transmission for entertainment or political purposes. While pirate just refers to the illegal nature of the broadcasts, there have also been notable pirate offshore radio transmissions.
Pirate radio generally describes the unlicensed broadcast of FM radio, AM radio, or short wave signals over a wide range. In some cases radio stations are deemed legal where the signal is transmitted, but illegal where the signals are received, especially when the signals cross a national boundary.
In other cases, a broadcast may be considered "pirate" due to the nature of its content, its transmission format or the transmit power of the station, even if the transmission is not technically illegal.
In the 1960’s, Pirate Radio boats in international waters would broadcast pop and rock to 10s of millions of British listeners.
The BBC, which then mostly catered to classical tastes, was forced to restructure and meet the demand for those genres. And thanks to this the modern radio was born!