n (obsolete) A rock; boulder; a hill.
n A visible mass of water droplets suspended in the air.
n Any mass of dust, steam or smoke resembling such a mass.
n Anything which makes things foggy or gloomy.
n (figurative) Anything unsubstantial.
n A dark spot on a lighter material or background.
n A group or swarm, especially suspended above the ground or flying.
n An elliptical shape or symbol whose outline is a series of semicircles, supposed to resemble a cloud.
n A telecom network (from their representation in engineering drawings)
n (computing, with "the") The Internet, regarded as an abstract amorphous omnipresent space for processing and storage, the focus of cloud computing.
n (figuratively) A negative or foreboding aspect of something positive: see every cloud has a silver lining or every silver lining has a cloud.
n (slang) Crystal methamphetamine.
n A large, loosely-knitted headscarf worn by women.
v (intransitive) To become foggy or gloomy, or obscured from sight.
v (transitive) To overspread or hide with a cloud or clouds.
v Of the breath, to become cloud; to turn into mist.
v (transitive) To make obscure.
v (transitive) To make less acute or perceptive.
v (transitive) To make gloomy or sullen.
v (transitive) To blacken; to sully; to stain; to tarnish (reputation or character).
v (transitive) To mark with, or darken in, veins or sports; to variegate with colors.
v (intransitive) To become marked, darkened or variegated in this way.
n A surname.