Source : Webster's Revised Unabridged Dictionary (1913)

Precipitation \Pre*cip`i*ta"tion\, n. (Meteor.)
   A deposit on the earth of hail, mist, rain, sleet, or snow;
   also, the quantity of water deposited.

   Note: Deposits of dew, fog, and frost are not regarded by the
         United States Weather Bureau as precipitation. Sleet
         and snow are melted, and the record of precipitation
         shows the depth of the horizontal layers of water in
         hundredths of an inch or in millimeters.

Precipitation \Pre*cip`i*ta"tion\, n. [L. praecipitatio: cf. F.
   pr['e]cipitation.]
   1. The act of precipitating, or the state of being
      precipitated, or thrown headlong.

            In peril of precipitation From off rock Tarpeian.
                                                  --Shak.

   2. A falling, flowing, or rushing downward with violence and
      rapidity.

            The hurry, precipitation, and rapid motion of the
            water, returning . . . towards the sea. --Woodward.

   3. Great hurry; rash, tumultuous haste; impetuosity. ``The
      precipitation of inexperience.'' --Rambler.

   4. (Chem.) The act or process of precipitating from a
      solution.

Source : WordNet®

precipitation
     n 1: the quantity of water falling to earth at a specific place
          within a specified period of time; "the storm brought
          several inches of precipitation"
     2: the process of forming a chemical precipitate
     3: the falling to earth of any form of water (rain or snow or
        hail or sleet or mist) [syn: {downfall}]
     4: the act of casting down or falling headlong from a height
     5: an unexpected acceleration or hastening; "he is responsible
        for the precipitation of his own demise"
     6: overly eager speed (and possible carelessness); "he soon
        regretted his haste" [syn: {haste}, {hastiness}, {hurry},
        {hurriedness}]