From the Oxford English Dictionary.

Addendum: The term itself was perhaps first used by ethologist Richard Dawkins in his classic book on the code's point of view, "The Selfish Gene", and was meant to include almost any patterns that one can re-apply or mimic, ranging from styles of movement, dress, interaction, and vocal phrasing; through codes of law, ethics, and professional conduct; to our paradigms of religious belief and scientific understanding. For a primer on the subject, the Meme Lab in Bristol is one place to go.

Extension: We use the term "we-meme" to refer to that subset of all replicable patterns (the full set of memes) which are relevant for, helpful to, enjoyable by, or at least for some reason supported thanks to, in particular organisms in groups.