Sinkholes

noun

1. A hole formed in soluble rock by the action of water, serving to conduct surface water to an underground passage
2. A depressed area in which waste or drainage collects.
3. A hole in the playfield that rewards the player when the ball is guided into it.
4. A domain name server that has been configured to hand out non-routeable addresses for all domains, so that every computer that uses it will fail to get access to the real website.
5. An attack which redirects requests - be it network or memory accesses - to a new location defined by the attacker.