an idea, behavior, style, or usage that spreads from person to person within a culture 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 (the guy that actually came up with the word back in 1976)