A luminous cloud of a kind occasionally seen at night in summer in high latitudes, at the altitude of the mesopause: he estimated the height of the noctilucent clouds he saw at 80 to 100 km
More example sentences
- One of them is something that I've never actually seen but I had seen pictures of; it's a thing called a noctilucent cloud, this is a cloud that occurs at about 86 kilometres, it may be present more often than we see it.
- ‘Humbug’ refers to natural phenomena such as heavenly bodies, noctilucent clouds, ball lightning, and man-made objects such as glowing blimps.
- Evidence of these changes comes from sightings of noctilucent clouds, very unusual clouds seen only in polar regions and known to be in the mesosphere.
late 19th century: from Latin nox, noct- 'night' + lucere 'to shine' + -ent.
Definition of noctilucent cloud in:
- The US English dictionary