Unpublished means not made public. If your phone number is unpublished, it’s not listed in the telephone directory and you’re safe from late-night calls from long-lost boyfriends.
If you’re scrounging around in an old desk drawer and stumble upon an unpublished poem by Emily Dickinson, your discovery is likely to make you famous. A painting or a piece of music can also be described as unpublished if no one has written about it or put it into some kind of form available to a wider audience. If you're an aspiring author but nothing you've written has appeared in print yet, you're an unpublished author.