a collection of visible vapor, or watery particles, suspended in the upper atmosphere.-a mass or volume of smoke, or flying dust, resembling vapor.-a dark vein or spot on a lighter material, as in marble; hence, a blemish or defect; as, a cloud upon one's reputation; a cloud on a title.-that which has a dark, lowering, or threatening aspect; that which temporarily overshadows, obscures, or depresses; as, a cloud of sorrow; a cloud of war; a cloud upon the intellect.-a great crowd or multitude; a vast collection.-a large, loosely-knitted scarf, worn by women about the head.-to overspread or hide with a cloud or clouds; as, the sky is clouded.-to darken or obscure, as if by hiding or enveloping with a cloud; hence, to render gloomy or sullen.-to blacken; to sully; to stain; to tarnish; to damage; -- esp. used of reputation or character.-to mark with, or darken in, veins or sports; to variegate with colors; as, to cloud yarn.-to grow cloudy; to become obscure with clouds; -- often used with up.