Source : Webster's Revised Unabridged Dictionary (1913)

Rain \Rain\, n. & v.
   Reign. [Obs.] --Spenser.

Rain \Rain\, n. [OF. rein, AS. regen; akin to OFries. rein, D. &
   G. regen, OS. & OHG. regan, Icel., Dan., & Sw. regn, Goth.
   rign, and prob. to L. rigare to water, to wet; cf. Gr. ? to
   wet, to rain.]
   Water falling in drops from the clouds; the descent of water
   from the clouds in drops.

         Rain is water by the heat of the sun divided into very
         small parts ascending in the air, till, encountering
         the cold, it be condensed into clouds, and descends in
         drops.                                   --Ray.

         Fair days have oft contracted wind and rain. --Milton.

   Note: Rain is distinguished from mist by the size of the
         drops, which are distinctly visible. When water falls
         in very small drops or particles, it is called mist;
         and fog is composed of particles so fine as to be not
         only individually indistinguishable, but to float or be
         suspended in the air. See {Fog}, and {Mist}.

   {Rain band} (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.

   {Rain bird} (Zo["o]l.), the yaffle, or green woodpecker.
      [Prov. Eng.] The name is also applied to various other
      birds, as to {Saurothera vetula} of the West Indies.

   {Rain fowl} (Zo["o]l.), the channel-bill cuckoo ({Scythrops
      Nov[ae]-Hollandi[ae]}) of Australia.

   {Rain gauge}, an instrument of various forms measuring the
      quantity of rain that falls at any given place in a given
      time; a pluviometer; an ombrometer.

   {Rain goose} (Zo["o]l.), the red-throated diver, or loon.
      [Prov. Eng.]

   {Rain prints} (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.

   {Rain quail}. (Zo["o]l.) See {Quail}, n., 1.

   {Rain water}, water that has fallen from the clouds in rain.

Rain \Rain\, v. i. [imp. & p. p. {Rained}; p. pr. & vb. n.
   {Raining}.] [AS. regnian, akin to G. regnen, Goth. rignjan.
   See {Rain}, n.]
   1. To fall in drops from the clouds, as water; used mostly
      with it for a nominative; as, it rains.

            The rain it raineth every day.        --Shak.

   2. To fall or drop like water from the clouds; as, tears
      rained from their eyes.

Rain \Rain\, v. t.
   1. To pour or shower down from above, like rain from the
      clouds.

            Then said the Lord unto Moses, Behold, I will rain
            bread from heaven for you.            --Ex. xvi. 4.

   2. To bestow in a profuse or abundant manner; as, to rain
      favors upon a person.

Source : WordNet®

rain
     v : precipitate as rain; "If it rains much more, we can expect
         some flooding" [syn: {rain down}]

rain
     n 1: water falling in drops from vapor condensed in the
          atmosphere [syn: {rainfall}]
     2: drops of fresh water that fall as precipitation from clouds
        [syn: {rainwater}]
     3: anything happening rapidly or in quick successive; "a rain
        of bullets"; "a pelting of insults" [syn: {pelting}]