资料来源 : Webster's Revised Unabridged Dictionary (1913)

Warning \Warn"ing\, a.
   Giving previous notice; cautioning; admonishing; as, a
   warning voice.

         That warning timepiece never ceased.     --Longfellow.

   {Warning piece}, {Warning wheel} (Horol.), a piece or wheel
      which produces a sound shortly before the clock strikes.