basal plane

from The Collaborative International Dictionary of English v.0.48

Basal \Ba"sal\, a.
   Relating to, or forming, the base.
   [1913 Webster]

   {Basal cleavage}. See under {Cleavage}.

   {Basal plane} (Crystallog.), a plane parallel to the lateral
      or horizontal axis.
      [1913 Webster]