This is the phenomenon
where you find yourself knowing things about stuff. Stuff that you haven't experienced yourself, but you encounter from so many outlets that you can't help absorbing it yourself. This will happen to you from the moment you are born, but you probably won't notice it. Everyone will have their own examples of this but for me the one thing I've always been aware of without knowing where from, is songs by the Beatles
Yellow Submarine, Help!, A Day in the Life, Yesterday. I've known these songs all my life and I can never remember not knowing them. They must have been played so often on the tv, radio, and been such general background noise that I assimilated them and made Lennon and McCartney a part of me forever. It also makes me remember tales of Freddy Krueger circulating around the playground depsite their being no one in my class who had seen Nightmare on Elm Street
But this osmosis doesn't just stop at childhood. It is reinforced all the time by the people you meeet, overheard conversations on the bus, adverts for televison programmes you don't want to watch. This form of cultural osmosis will make you aware of things you don't want to know about, the tabloid culture of celebrities famous for famous. You will become familiar with celebrity chefs whether you like it or not and wannabe pop stars striving to extend their fifteen minutes of fame will imprint themselves on your consciousness. There is nothing you can do about it without immersing yourself away from modern society. No doubt this is happening accross the world, but the specifics will be different if you are in Japan or the USA.
Cultural osmosis also has wider implications then what weather forecaster is currently wowing the nation. This occurs when different, well, cultures interact for a variety of reasons, most typically immigration either for ecomonic or political reasons. The United States in particular has spent much of its history welcoming proto-citizens from different cultures, but it has and will remain a worldwide phenomenon. What will happen is the less dominant culture will slowly adapt their behaviour to conform to the prevalent moral and day to day behaviour that is the norm in the dominant culture. This will usually occur down through the generations, although it will also work in reverse, and is generally a mechanism for reducing prejudice and hatred between people of different backgrounds. However when the cultures are kept apart or are segregated for whatever reason, as in Palestine/Israel or Northern Island, the process of cultural osmosis slows down or even suffers paralysis, and is unable to reverse the wounds and hatred that have been sown down from generations past.
Whatever you define cultural osmosis as, the term has entered into use to describe all the situations described above, and the adoption of the term itself is a sign of its efectiveness and relevance in describing features of modern society.