a visible collection of particles of water or ice suspended in the air, usually at an elevation above the earth's surface.
2.
any similar mass, especially of smoke or dust.
3.
a dim or obscure area in something otherwise clear or transparent.
4.
a patch or spot differing in color from the surrounding surface.
5.
anything that obscures or darkens something, or causes gloom, trouble, suspicion, disgrace, etc.