noun \ ˈmēm \
Definition of meme
Information that presents an idea, behavior, style, or usage in a form that can be communicated by a person to other people within a society.
Memes are part of the culture, the building blocks of knowledge. Not every piece of information is a meme. In order to become a meme, the thought, idea or behavior must be presented in a form it can be communicated to others.
Richard Dawkins has invented the term to create parallel between the driver of biological evolution (gene) and the driver of the cultural evolution (meme):
Memes (discrete units of knowledge, gossip, jokes and so on) are to culture what genes are to life. Just as biological evolution is driven by the survival of the fittest genes in the gene pool, cultural evolution may be driven by the most successful memes. —Richard Dawkins