(Or outernet meme) A meme that gained popularity by distribution outside the internet.
The word "extranet" is a retronym - a word used to describe an object or entity that has been superseded by a new kind of thing, where the original object or entity was not previously described using the new word.
Examples: email and snail mail (snail mail being the retronym for ordinary "mail"); quantum mechanics and classical mechanics (before the discovery of quantum mechanics the way matter interacts on the superatomic scale was simply "mechanics"); and finally, internet meme and extranet meme.
Examples of popular extranet memes:
Keep Calm and Carry On
Pretty much any idea that became widespread without using the Internet.