n (philosophy) Any unit of cultural information, such as a practice or idea, that is transmitted verbally or by repeated action from one mind to another.
n (philosophy) A self-propagate | propagating unit of cultural evolution having a resemblance to the gene (the unit of genetics).
n (Internet|slang) A quiz or survey that is copied from one webpage or online journal to another, each participant filling in his or her personal answers.
n (Internet|slang) A thought, idea, joke, or concept that spreads online, often virally. Can be in the form of an image, a video, an email, an animation, or music.