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.
Full Definition of RAIN. 1. a: water falling in drops condensed from vapor in the atmosphere b: the descent of this water c: water that has fallen as rain: rainwater. 2. a: a fall of rain: rainstorm b plural: the rainy season. 3. : rainy weather. 4.