MEME 1 : an idea, belief or belief system, or pattern of behavior that spreads throughout a culture either vertically by cultural inheritance (as by parents to children) or horizontally by cultural acquisition (as by peers, information media, and entertainment media)
An Internet meme (/ˈmiːm/ MEEM) is a concept that spreads from person to person via the Internet.1 The word meme was coined by Richard Dawkins in his 1976 book The Selfish Gene, as an attempt to explain the way cultural information spreads;2 internet memes are a subset of this, specific to the culture and environment of the internet.
Fads and sensations tend to grow rapidly on the Internet, because the instant communication facilitates word of mouth transmission.
I had to look this up too. Kind of lame, imho.