Source : Webster's Revised Unabridged Dictionary (1913)

Stack \Stack\, v. t. [imp. & p. p. {Stacked}; p. pr. & vb. n.
   {Stacking}.] [Cf. Sw. stacka, Dan. stakke. See {Stack}, n.]
   To lay in a conical or other pile; to make into a large pile;
   as, to stack hay, cornstalks, or grain; to stack or place
   wood.

   {To stack arms} (Mil.), to set up a number of muskets or
      rifles together, with the bayonets crossing one another,
      and forming a sort of conical pile.