I've been around this site for a while, reading other people's stories, and I finally decided to share my own experience. I had rarely shared this story with others, because all I've got in answer were laughs and skeptical stares.
It happened a lot of years ago, when I was between 7 and 10 years old, but I remember it very clearly, like it happened only a few weeks ago.
That day I was at my Grandma's, wandering in the garden, searching for something to do. The garden is very big, with the back side 3 or 4 times larger than the front one, surrounded by a tall wire fence and strewn with hazels and many others fruit trees and flower beds.
I was walking in the middle of the back side toward the end of it. Overe there, on the extreme edge of the fence, there is a gate confining with another part of the garden which isn't fenced and resembles a little wood. I always liked to go there for climbing trees, hiding in the tall grass and searching for little animal bones left on the ground by owls.
Well, I was there walking, when I saw a white cat staring at me a few meters ahead. I always loved cats, so I tried to slowly getting closer, hoping that it will let me pet it. I remember it was a quite big cat but I was a little girl, so I can't say how bigger from a normal cat it was. It took a couple of steps in my direction, then, when it find out I was walking in its direction, it turned the back on me and started walking very slowly toward the fence, stopping every once in a while to look at me, as it was expecting me to follow. It doesn't walk like a normal cat, it was... Smoky? It's silhouette was slightly flickering and waving, like it was actually made of white thick smoke, its muzzle was kind of blurred out and the grass didn't bend under it's paws, like it didn't have weight nor consistency.
When it reached the fence it hid behind the trunk of a little tree. I went there to catch it, but as I reached the tree it was disappeared.
The tree was very small and had very few leaves, so I'd totally spotted it out if it was trying to hid between the branches. The fence is about 3 meters tall, and the view was clear, and I swear I didn't see nothing at all jumping or climbing on it, also the weren't others trees/plants there and the neighbor's garden was empty with freshly cut grass. There were absolutely nothing in which a big white cat could hide.
For some reason I didn't believed for a single moment it was a normal and a living cat, I immediately realized that there was something strange with that, but, I don't know why, at that time I didn't mind it and I act like I was facing a normal cat, maybe only being a little more curious than usual.
Some time later I knew that my Grandmother used to bury her dead cats a couple of meters ahead from where the white big smoky cat vanished.