The Collaborative International Dictionary of English v.0.48:

Hill \Hill\, v. t. [imp. & p. p. Hilled; p. pr. & vb. n.
   Hilling.]
   To surround with earth; to heap or draw earth around or upon;
   as, to hill corn.
   [1913 Webster]

         Showing them how to plant and hill it.   --Palfrey.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Hilling \Hill"ing\, n.
   The act or process of heaping or drawing earth around plants.
   [1913 Webster]