a black hole is not an antimeme, but it has antimemetic properties; its boundary is a information diode. bits that cross the Schwartzchild radius do not make it back out
similarly, secret-keepers are not antimemes, but possess antimemetic properties, albeit less binary ones
a perfect secret-keeper's information flux boundary is also a memetic diode; memes go in but don't go out, besides under very specific conditions
mostly nothing is a perfect secret-keeper, the diode being probabilistic. this applies to people, organizations, and deathtraps