The movie "Animal House" premiered in 1978 and a year or so later was on TV. The TV showing was preceded by this caution: "The following program is intended for mature audiences only" (this was before the TV ratings system, boys and girls, so we had no alphabetic clue if we were being protected from violence, or sexual content or badly-overdubbed forbidden words). Now, I had seen Animal House in the theater and, the way I remembered it, it appealed more to immature audiences: those of us who could watch a man imitate a zit by spitting mashed potatoes on a prissy sorority girl and understand the humor in that.
The network people who attached the "mature audience" warning to the movie were using definition 8 of "mature": "composed of adults, considered as being less susceptible to (less able to be affected emotionally by) explicit sexual content, violence, or obscene language, as of a film or stage performance." By that definition, mature people would not laugh at a horse being shot to death in a college dean's office. I, however, thought it was hilarious (even though I was technically a 20-something-year-old adult).
So what did they really mean? They meant the movie was intended for sophmoric, crude, puerile people over 18, because we want to hide those traits fom those under 18, in whom we might still be able to repress them by means of forced church atendance, restrictive, modest, "appropriate" clothing and personal hygiene classes in public schools. Our hope was that by keeping young people from movies like "Animal House" we could raise a generation of adults who could hear the word "penis" and not giggle. Judging by movies today, our efforts weren't worth shit (**immature crowd reacts wildly to last word**).
Over at Humor Blogs, my blog is shown with a haloed smiley face, meaning "This site generally does not contain 'mature' content". Mature is appropriately in quotation marks because they just mean there are no boobies or bloody bodies or bad words. They don't mean that mature discussions of politics and language faux pas appeal to the same mature audience as "American Pie", "Jackass" or "Porky's". I think they mean my posts are not "3. fully developed" or "5. completed, perfected." I contend that my writing is mature in that it has "6.little or no potential for further growth."
"mature content" = "a ten ton rectum"