noun

• (meteorology) Condensed water falling from a cloud.
  "We've been having a lot of rain lately."
• (figuratively) Any matter moving or falling, usually through air, and especially if liquid or otherwise figuratively identifiable with raindrops.
• (figuratively) An instance of particles or larger pieces of matter moving or falling through air.
  "A rain of mortar fire fell on our trenches."

verb

• (impersonal, meteorology) To have rain fall from the sky.
  "Judging by the black cloud, it will rain later today."
• (intransitive, figuratively) To fall as or like rain.
  "Tears rained from her eyes."
• (transitive, figuratively) To issue (something) in large quantities.
  "The boxer rained punches on his opponent's head."