strato-cumulus (adj.)

before vowels strat-, word-forming element referring to layers or layering, also stratus clouds, from combining form of Latin stratus "a spreading," from PIE root *stere- "to spread."

1650s, "a heap," from Latin cumulus "a heap, pile, mass, surplus," from PIE *ku-m-olo-, suffixed shortened form of root *keue- "to swell." Meteorological use for "rounded mass of clouds, snowy white at the top with a darker, horizontal base" is attested by 1803.