Definitions
1.NounA meme deployed to nullify or protect against another meme.
2.NounA unit of information that prevents itself from being spread, either due to its contents, (e.g, a password or encrypted document,) or a secondary mechanism that prevents its transmission. (e.g, by erasing itself from any mind that it enters.)
3.NounAn image macro which intentionally subverts one's expectations by not including a joke; a meme antijoke.