When you have a dream that you see a black rabbit, what this means is that you have found something elusive. Black rabbits are some of the best animals at remaining camouflaged in their natural environments. If they are in the forest, they have much more cover in the shadows and under piles of leaves than white rabbits do, since white rabbits stick out like a sore thumb and black rabbits can blend into their surroundings. In addition rabbits also live in holes that they dig for themselves, so a black rabbit has even more cover underground when you can't separate its body in a crevice from another diverging path in the dirt.
Basically, the point of all that rambling is that rabbits are hard to catch; and black rabbits are even harder to catch. When you dream that you sight or that you catch a black rabbit it means that you have finally found the answer to a question that has been eluding you for some time. You have finally figured out something that you needed to know for a while and you have finally got a grasp on things yourself. This could be the type of thing that took you a long time to figure out or it could be the type of thing that you found the answer to relatively shortly. But either way, I was a question that had been vexing you and you finally found the answer. It could also be you found a literal item that you had been looking for, for some time too.
To dream that you are a black rabbit means that you feel cowardly. The rabbit is not necessarily afraid so much as it is very skittish. A black rabbit is both invisible to us and skittish. It is not actually invisible, just very hard to see, and thus it feels as if it is not even there at all. When you feel invisible it is because you feel that you are not making a dent on society, you are not making a change which you see as integral to the experience of life. You feel as though people look right through you when they are talking to you rather than actually paying attention to you.
Combine this with your naturally scared personality, and nobody will ever be able to get close to you. You close yourself off and shut yourself down so that nobody can reach you deep down. You hide yourself from others and do so because you are scared of being judged, yet it is exactly this attitude of fear which causes them to judge you. You need to try and make yourself stand out more to the general population, and especially to your friends if they are a group that you think has trouble noticing you too. Otherwise you will always blend into the background and your worst dreams will be proven true. Don't let yourself go unnoticed.