The Collaborative International Dictionary of English v.0.48:

Fluidal \Flu"id*al\, a.
   Pertaining to a fluid, or to its flowing motion.
   [1913 Webster]

   Fluidal structure (Geol.), the structure characteristic of
      certain volcanic rocks in which the arrangement of the
      minute crystals shows the lines of flow of thew molten
      material before solidification; -- also called fluxion
      structure.
      [1913 Webster]