blackhole

Noun

black hole (plural black holes)

1. A place of punitive confinement; a lockup or cell; a military guardroom.
   • ‘I will convince you that I do know [my duty] by clapping you for the remainder of the night into the black hole, young gentleman, do you see, and have no doubt but the air of that agreeable apartment will restore your senses.’1808–10, William Hickey, Memoirs of a Georgian Rake, Folio Society 1995, p. 282
2. A region of spacetime that exerts a gravitational pull strong enough that no matter or energy, not even light, can escape it.
   • Astronomers have captured the first image of a black hole, heralding a revolution in our understanding of the universe’s most enigmatic objects.2019 April 10, Hannah Devlin, The Guardian
3. (figuratively) A void into which things disappear for good; an inscrutable area or subject.
   • you'll have to love U.S. District Court Judge John Kane's decision to keep Denver-based Exactis.com out of an Internet black hole.... MAPS maintains a database of Internet addresses that it believes send or relay spam. It’s called the "Realtime Blackhole List"2000 November 26, Linda Seebach, “Unwanted e-mail belongs in an Internet black hole”, in RockyMountainNews.com
4. A dangerous optical illusion that can occur on a nighttime approach with dark, featureless terrain between the aircraft and a brightly-lit runway, where the aircraft appears to the pilots to be higher up than it actually is, potentially triggering a premature or overly-steep descent and a crash short of the runway.
5. (Internet, attributive, often) A place where incoming traffic is silently discarded.
   • One way of fighting spam is to use a blackhole list maintained on a blackhole server.
6. A bit bucket; a place of permanent oblivion for data.

See all 7 meanings of black hole