Some hour after midnight around 2 or 3am in the US, not sure if there's certain days of the week (perhaps not on weekends when a lot of people are up), they're allowed to play a lot of uncensored content on the radio. Many radio stations don't though. Depends on the programming. The idea is that children are sleeping during those hours to not hear it. They broadcast this disclaimer about the FCC. You'd have only come across this if your schedule has you up during these hours listening to the car radio, by tuning radio stations to listen to. I've never run into this any other time, even after I heard it on the radio. It's because you'd have to activately be tuning in on it, during these hours, and there's limited programming that does this. The content is something which you would hear from a CD with the "parental advisory" label or XM/Sirius radio
Wild would be like the dark web though, as opposed to rated R or parental advisory.
Then, there's amateur ham radio. There's less rules for how to broadcast, as anyone can without a license, though, I'm unsure about censored content there. Unless there's unlawful activity, no one would bother to regulate that. FreeBSD magazine has an article about amateur ham radio, but not this aspect of it.