The Collaborative International Dictionary of English v.0.48:

Pluvial \Plu"vi*al\, n. [LL. pluviale a garment which keeps off
   the rain: cf. F. pluvial.]
   A priest's cope.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Pluvial \Plu"vi*al\, a. [L. pluvialis, fr. pluvia rain: cf. F.
   pluvial. See Plover.]
   1. Of or pertaining to rain; rainy. [R.]
      [1913 Webster]

   2. (Geol.) Produced by the action of rain.
      [1913 Webster]