combining form of CUMULUS, used in naming cloud-forms which combine the cumulus with other types: e.g., Cumulo-stratus, Cumulo-cirro-stratus: see quots.
1803. L. Howard, Modif. Clouds (1865), 4. Cumulo-stratus.… The Cirro-stratus blended with the Cumulus, and either appearing intermixed with the heaps of the latter or superadding a wide-spread structure to its base.
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.
1815. T. Forster, Atmospheric Phaenom. (ed. 2), 150. The cumulostratus being a state of the clouds going on to become nimbus.
1856. Scoffern & Lowe, Pract. Meteorol., 55. Cumulo stratus. This compound cloud chiefly appears towards night in dry windy weather, and is of a leaden colour.
