It is commonly called alumina, and may also be called aloxide, aloxite, or alundum depending on particular forms or applications. It commonly occurs in its crystalline polymorphic phase Î±-Al 2 O 3, in which it composes the mineral corundum, varieties of which form the precious gemstones ruby and sapphire.
rain cloud. (meteorology). Any cloud from which rain falls; a popular term having no technical denotation. 1  Facebook. 2  Twitter.
Cumulonimbus: nimbus with cumuliform characteristics. Nimbus is Latin for cloud - in meteorology, nimbus means specifically rain cloud - cumulonimbus are large storm clouds, often thunderclouds. Cirrocumulus: cirrus with small globular elements (instead of being wispy or sheet-like).ileus: Latin for cap, the pileus is a small cloud which forms a cap on the top of a cumuliform cloud. Velum: Latin for ship's sail or tent flap, a velum is a horizontal, veil-like cloud which a cumuliform cloud may pierce.