space jellyfish

noun

An atmospheric phenomenon of the early morning or late evening, where the ground is in nighttime, but sunlight shines through the upper atmosphere, whereby rocket exhaust, the rocket plume, expanding in the upper atmosphere reflects light, creating a visual appearance similar to that of a jellyfish. It can result in reports of UFO sightings.

Meanings

nounspace jellyfish (plural space jellyfishes or space jellyfish)

plural space jellyfishes

  1. informalspace flightaerospaceAn atmospheric phenomenon of the early morning or late evening, where the ground is in nighttime, but sunlight shines through the upper atmosphere, whereby rocket exhaust, the rocket plume, expanding in the upper atmosphere reflects light, creating a visual appearance similar to that of a jellyfish. It can result in reports of UFO sightings.
  2. informalspace flightaerospaceAn atmospheric phenomenon of the moon-lit nighttime, whereby expanding rocket exhaust in the night sky reflects moonlight, creating the appearance similar to that of a jellyfish.
  3. informalspace flightaerospaceAn atmospheric phenomenon of the high latitude polar night, where a nighttime high latitude polar rocket launch directed towards even higher latitudes polewards, emerges from Earth's shadow, reflecting light streaming over the poles back into the Earthly night, creating lit expanding rocket exhaust resembling a jellyfish.

Synonyms & antonyms

Origin

space + jellyfish. From having a jellyfish-like appearance, and being in the sky.

Full word history & related roots →
Cite this entry
APA

space jellyfish. (n.d.). In WatkinsX Dictionary. Retrieved November 4, 2026, from https://dictionary.watkinsx.com/word/space%20jellyfish

MLA

“space jellyfish.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/space%20jellyfish. Accessed November 4, 2026.

Chicago

WatkinsX Dictionary, s.v. “space jellyfish,” accessed November 4, 2026, https://dictionary.watkinsx.com/word/space%20jellyfish.

Source: space jellyfish on Wiktionary, CC BY-SA 4.0.