The Collaborative International Dictionary of English v.0.48:

Hydrometeor \Hy`dro*me"te*or\, n. [Hydro-, 1 + meteor.]
   A meteor or atmospheric phenomenon dependent upon the vapor
   of water; -- in the pl., a general term for the whole aqueous
   phenomena of the atmosphere, as rain, snow, hail, etc.
   --Nichol.
   [1913 Webster]