# black hole

Pronunciation: say "blak HOHL" US /blæk ˈhoʊl/, UK /blæk ˈhəʊl/

## Noun

1. A region of spacetime whose gravitational pull is so strong that no matter or energy, not even light, can escape from it.
   - Simple: An area in space where gravity pulls so hard that nothing, not even light, can get out.
   - _Astronomers detected X-rays from gas being pulled into a black hole at the heart of the galaxy._
   - _When a very massive star collapses at the end of its life, it can become a black hole._
2. A void into which things vanish for good, or an area or subject that is impossible to see into or understand.
   - Simple: A place where things disappear forever, or a subject or area that no one can understand.
   - _That committee is a black hole: proposals go in and nobody ever hears about them again._
   - _The decade before the census is a black hole in the town's history, with almost no records surviving._
3. A place where someone is confined as a punishment, such as a cell, a lockup, or a military guardroom.
   - Simple: A cell or room where someone is locked up as punishment, such as in a jail or on a military base.
   - _The sergeant ordered the drunken private confined to the black hole until morning._
   - _Boys who talked back to the schoolmaster were shut in the black hole for the afternoon._
4. A place on a network where incoming traffic is silently discarded instead of being delivered.
   - Simple: A place on a network where data sent to it is thrown away without any warning.
   - _The provider routed traffic from the attacking addresses into a black hole, so the flood of requests never reached the site._
   - _Our mail server checks every sender against a black hole list before accepting a message._

## Verb

5. To redirect network traffic or similar data so that it goes nowhere, or to discard incoming traffic.
   - Simple: To send network data nowhere, or to throw away data that is coming in.
   - _We asked our upstream provider to black hole the attacked prefix until the flood died down._
   - _The mail server black holes messages from known spam sources instead of bouncing them back._

## Other meanings

- (noun) A bit bucket; a place of permanent oblivion for data.
- (noun) 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.

## Origin

In its physical sense (a region of spacetime with extreme gravitational pull), physicist Hong-Yee Chiu attributed the term to his colleague Robert H. Dicke, who around 1960–1961 compared these objects to the Black Hole of Calcutta. It first appeared in print in 1964 in writing by journalist Ann Ewing, and its widespread popularization is generally credited to a 1967 lecture by physicist John Wheeler.

Source: DictionaryAI, https://dictionaryai.com/define/black-hole (written from Wiktionary data, CC BY-SA 4.0: https://creativecommons.org/licenses/by-sa/4.0/).