Memes are thoughts, ideas, opinions that spread through a fairly large population like an organism similar to a virus. A joke or (e.g. political) one-liner that goes viral is an example. A striking image can be a meme as well. And in the same vein so can a gif image. Obviously due to arguable 'misuse' of the word, its most popular interpretation is much narrower, namely that of a particular kind of image containing (usually) some witty text or (very occasionally) an insightful idea. Whether or not a gif image classifies as a meme within this narrow definition, I'm not sure. But I am sure I don't care; and neither should anyone else.
