n.     A unit of cultural information, such as a cultural practice or idea, that is transmitted verbally or by repeated action from one mind to another.

Source: The American Heritage@reg; Dictionary of the English Language, Fourth Edition
Copyright© 2000 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.

..Or, in plain english: "a thought virus". An internet meme is a meme that most likely has originated on the internet and spreads via the internet. Several examples of internet memes are: "All Your Base Are Belong To Us", "I kiss you", "Bananna Phone", "Badger badger badger", Gonads and Strife, Racecar insanity test, I work at burger king, peanut butter jelly time