rain

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Water condensed from atmospheric vapor and falling in drops.
• noun A fall of such water; a rainstorm.
• noun The descent of such water.
• noun Rainy weather.
• noun A rainy season.
• noun A heavy or abundant fall.
• intransitive verb To fall in drops of water from the clouds.
• intransitive verb To fall like rain.
• intransitive verb To release rain.
• intransitive verb To send or pour down.
• intransitive verb To give abundantly; shower.
• idiom (rain cats and dogs) To rain very heavily.

from The Century Dictionary.

• To fall in drops through the air, as water: generally used impersonally.
• To fall or drop like rain; as, tears rained from their eyes.
• To pour or shower down, like rain from the clouds; pour or send down abundantly.
• noun An obsolete spelling of rein.
• noun A ridge.
• noun A furrow.
• noun The descent of water in drops through the atmosphere, or the water thus falling.
• noun Figuratively— A fall of any substance through the atmosphere in the manner of rain, as of blossoms or of the pyrotechnic stars from rockets and other fireworks.
• noun A shower, downpour, or abundant outpouring of anything.
• noun Synonyms Rain, Haze, Fog, Mist, Cloud. A cloud resting upon the earth is called mist or fog. In mist the globules are very fine, but are separately distinguishable, and have a visible motion. In fog the particles are separately indistinguishable, and there is no perceptible motion. A dry fog is composed largely of dust-particles on which the condensed vapor is too slight to occasion any sense of moisture. Haze differs from fog and cloud in the greater microscopic minuteness of its particles. It is visible only as a want of transparency of the atmosphere, and in general exhibits neither form, boundary, nor locus. Thus, among haze, fog, mist, and rain, the size of the constituent particles or globules is a discriminating characteristic, though frequently cloud merges into fog or mist, and mist into rain, by insensible gradations.

from the GNU version of the Collaborative International Dictionary of English.

• intransitive verb To fall in drops from the clouds, as water; -- used mostly with it for a nominative.
• intransitive verb To fall or drop like water from the clouds.
• transitive verb To pour or shower down from above, like rain from the clouds.
• transitive verb To bestow in a profuse or abundant manner.
• obsolete Reign.
• noun Water falling in drops from the clouds; the descent of water from the clouds in drops.
• noun (Meteorol.) a dark band in the yellow portion of the solar spectrum near the sodium line, caused by the presence of watery vapor in the atmosphere, and hence sometimes used in weather predictions.
• noun (Zoöl.) the yaffle, or green woodpecker. [Prov. Eng.] The name is also applied to various other birds, as to Saurothera vetula of the West Indies.
• noun (Zoöl.) the channel-bill cuckoo (Scythrops Novæ-Hollandiæ) of Australia.
• noun an instrument of various forms for measuring the quantity of rain that falls at any given place in a given time; a pluviometer; an ombrometer.
• noun (Zoöl.), [Prov. Eng.] the red-throated diver, or loon.
• noun (Geol.) markings on the surfaces of stratified rocks, presenting an appearance similar to those made by rain on mud and sand, and believed to have been so produced.
• noun (Zoöl.) See Quail, n., 1.
• noun water that has fallen from the clouds in rain.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Condensed water falling from a cloud.
• noun figuratively Any matter moving or falling, usually through air, and especially if liquid or otherwise figuratively identifiable with raindrops.
• noun figuratively An instance of particles or larger pieces of matter moving or falling through air.
• verb impersonal To have rain fall from the sky.
• verb intransitive To fall in large quantities.
• verb transitive To issue (something) in large quantities.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun water falling in drops from vapor condensed in the atmosphere
• noun anything happening rapidly or in quick successive
• noun drops of fresh water that fall as precipitation from clouds
• verb precipitate as rain