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.
1. (Physical Geography). a. precipitation from clouds in the form of drops of water, formed by the condensation of water vapour in the atmosphere. b. a fall of rain; shower. c. (in combination): a raindrop. hyetalpluvious. 2. a large quantity of anything falling rapidly or in quick succession: a rain of abuse.