nimbus

noun

Etymology: Learned borrowing from Latin nimbus (“dark cloud”). Doublet of nimb. Sense 2 (“grey rain cloud”) was coined by the British chemist and amateur meteorologist Luke Howard (1772–1864): see the 1803 quotation.

1. A circle of light; a halo.
2. A grey rain cloud.

   “[pages 99–100] Cumulo-cirro-stratus vel Nimbus. […] The rain cloud. A cloud or system of clouds from which rain is falling. It is a horizontal sheet, above which the cirrus spreads, while the cumulus enters it laterally and from beneath. […] [page 107] The nimbus, although in itself one of the least beautiful clouds, is yet now and then superbly decorated with its attendant the rainbow; which can only be seen in perfection when backed by the widely extended uniform gloom of this modification.”