The Collaborative International Dictionary of English v.0.48:

Liner \Lin"er\ (l[imac]n"[~e]r), n.
   1. One who lines, as, a liner of shoes or clothing.
      [1913 Webster]

   2. An airplane or ship belonging to a transportation company;
      also, a line-of-battle ship; a ship of the line.
      [1913 Webster]

   3. (Mach.) A thin piece placed between two parts to hold or
      adjust them, fill a space, etc.; a shim.
      [1913 Webster]

   4. A lining[2]. Specifically: (Steam Engine) A lining
      within the cylinder, in which the piston works and between
      which and the outer shell of the cylinder a space is left
      to form a steam jacket.
      [1913 Webster]

   5. A slab on which small pieces of marble, tile, etc., are
      fastened for grinding.
      [1913 Webster]

   6. (Baseball) A ball which, when struck, flies through the
      air in a nearly straight line not far from the ground;
      also called line drive; as, he hit a sharp liner to
      right.
      [1913 Webster]

   7. A protective envelope for a phonograph record or other
      object.
      [PJC]

   8. A lining; as, a removable coat liner.
      [PJC]

   9. Same as eyeliner.
      [PJC]

WordNet (r) 3.0 (2006):

liner
    n 1: (baseball) a hit that flies straight out from the batter;
         "the batter hit a liner to the shortstop" [syn: liner,
         line drive]
    2: a protective covering that protects an inside surface [syn:
       lining, liner]
    3: a piece of cloth that is used as the inside surface of a
       garment [syn: liner, lining]
    4: a large commercial ship (especially one that carries
       passengers on a regular schedule) [syn: liner, ocean
       liner]

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "liner":
   bush, bushing, doubling, doublure, facing, filler, filling,
   floating hotel, floating palace, inlay, inlayer, insole,
   interlineation, lining, ocean greyhound, ocean liner, packing,
   padding, passenger steamer, stuffing, wadding, wainscot