noun
pirate radio
Refers to unlicensed radio broadcasting, often from offshore stations or illegal transmitters.
1960年代、イギリスでは海賊放送が若者に人気だった。
In the 1960s, pirate radio was popular among young people in the UK.
海賊版 means 'pirated edition' (e.g., of software or books), while 海賊放送 specifically refers to unlicensed radio broadcasting.
Compound of 海賊 (pirate) and 放送 (broadcast), directly calqued from English 'pirate radio'.