ok so ya know how the deadpool list is full of videos people claim to be memes?
why dont you make a "video" section where people can post interesting videos INSTEAD OF POSTING IN MEMES?
another option:
before entering a meme you could have a "do you agree to these terms?" thingy.
it would say "pressing 'ok' means that you are fully aware of what a 'meme' is"
possibly a little quiz.
also:
when a new account is made you could have a lttle "definition of a meme" pop up or article for them to read before setting up the rest of the account.
these are just a few ideas that i got…