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.
cuÂ·muÂ·loÂ·nimÂ·bus. 1  the type of dense cloud that develops vertically through all cloud levels, consisting of water droplets, ice crystals, and sometimes hail, and associated with thunder, lightning, and heavy showers. noun.