The Collaborative International Dictionary of English v.0.48:

Cask \Cask\ (k[.a]sk), n. [Sp. casco potsherd, skull, helmet,
   prob. fr. cascar to break, fr. L. Quassure to break. Cf.
   Casque, Cass.]
   1. Same as Casque. [Obs.]
      [1913 Webster]

   2. A barrel-shaped vessel made of staves headings, and hoops,
      usually fitted together so as to hold liquids. It may be
      larger or smaller than a barrel.
      [1913 Webster]

   3. The quantity contained in a cask.
      [1913 Webster]

   4. A casket; a small box for jewels. [Obs.] --Shak.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Cask \Cask\, v. t.
   To put into a cask.
   [1913 Webster]

WordNet (r) 3.0 (2006):

cask
    n 1: the quantity a cask will hold [syn: cask, caskful]
    2: a cylindrical container that holds liquids [syn: barrel,
       cask]

Moby Thesaurus II by Grady Ward, 1.0:

45 Moby Thesaurus words for "cask":
   bag, barrel, basket, bole, bottle, box, box up, breaker, butt, can,
   capsule, carton, case, column, crate, cylinder, cylindroid, drum,
   encase, encyst, firkin, hamper, hogshead, jar, keg, kilderkin,
   pack, package, parcel, pillar, pipe, pot, puncheon, roll, roller,
   rouleau, rundlet, sack, tank, tin, trunk, tube, tun, vat,
   water butt