Source : Webster's Revised Unabridged Dictionary (1913)

Sack \Sack\ (s[scr]k), n. [OE. seck, F. sec dry (cf. Sp. seco,
   It. secco), from L. siccus dry, harsh; perhaps akin to Gr.
   'ischno`s, Skr. sikata sand, Ir. sesc dry, W. hysp. Cf.
   {Desiccate}.]
   A name formerly given to various dry Spanish wines. ``Sherris
   sack.'' --Shak.

   {Sack posset}, a posset made of sack, and some other
      ingredients.