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.
adj. cloudâ¢iâ¢er, cloudâ¢iâ¢est. 1. covered with clouds: a cloudy sky. 2. having little or no sunshine: a cloudy day. 3. of or like a cloud.