The Collaborative International Dictionary of English v.0.48:

ginmill \ginmill\, gin mill \gin mill\n.
   A commercial establishment where alcoholic drinks are served
   over a counter; a barroom; -- a disparaging term suggesting a
   cheap or disreputable bar.

   Syn: barroom, bar-room, bar, saloon, taproom.
        [WordNet 1.5 +PJC]

The Collaborative International Dictionary of English v.0.48:

Mill \Mill\, n. [OE. mille, melle, mulle, milne, AS. myln,
   mylen; akin to D. molen, G. m["u]hle, OHG. mul[imac],
   mul[imac]n, Icel. mylna; all prob. from L. molina, fr. mola
   millstone; prop., that which grinds, akin to molere to grind,
   Goth. malan, G. mahlen, and to E. meal. [root]108. See Meal
   flour, and cf. Moline.]
   [1913 Webster]
   1. A machine for grinding or comminuting any substance, as
      grain, by rubbing and crushing it between two hard, rough,
      or indented surfaces; as, a gristmill, a coffee mill; a
      bone mill.
      [1913 Webster]

   2. A machine used for expelling the juice, sap, etc., from
      vegetable tissues by pressure, or by pressure in
      combination with a grinding, or cutting process; as, a
      cider mill; a cane mill.
      [1913 Webster]

   3. A machine for grinding and polishing; as, a lapidary mill.
      [1913 Webster]

   4. A common name for various machines which produce a
      manufactured product, or change the form of a raw material
      by the continuous repetition of some simple action; as, a
      sawmill; a stamping mill, etc.
      [1913 Webster]

   5. A building or collection of buildings with machinery by
      which the processes of manufacturing are carried on; as, a
      cotton mill; a powder mill; a rolling mill.
      [1913 Webster]

   6. (Die Sinking) A hardened steel roller having a design in
      relief, used for imprinting a reversed copy of the design
      in a softer metal, as copper.
      [1913 Webster]

   7. (Mining)
      (a) An excavation in rock, transverse to the workings,
          from which material for filling is obtained.
      (b) A passage underground through which ore is shot.
          [1913 Webster]

   8. A milling cutter. See Illust. under Milling.
      [1913 Webster]

   9. A pugilistic encounter. [Cant] --R. D. Blackmore.
      [1913 Webster]

   10. Short for Treadmill.
       [Webster 1913 Suppl.]

   11. The raised or ridged edge or surface made in milling
       anything, as a coin or screw.
       [Webster 1913 Suppl.]

   12. A building or complex of buildings containing a mill[1]
       or other machinery to grind grains into flour.
       [PJC]

   Edge mill, Flint mill, etc. See under Edge, Flint,
      etc.

   Mill bar (Iron Works), a rough bar rolled or drawn directly
      from a bloom or puddle bar for conversion into merchant
      iron in the mill.

   Mill cinder, slag from a puddling furnace.

   Mill head, the head of water employed to turn the wheel of
      a mill.

   Mill pick, a pick for dressing millstones.

   Mill pond, a pond that supplies the water for a mill.

   Mill race, the canal in which water is conveyed to a mill
      wheel, or the current of water which drives the wheel.

   Mill tail, the water which flows from a mill wheel after
      turning it, or the channel in which the water flows.

   Mill tooth, a grinder or molar tooth.

   Mill wheel, the water wheel that drives the machinery of a
      mill.

   Gin mill, a tavern; a bar; a saloon; especially, a cheap or
      seedy establishment that serves liquor by the drink.

   Roller mill, a mill in which flour or meal is made by
      crushing grain between rollers.

   Stamp mill (Mining), a mill in which ore is crushed by
      stamps.

   To go through the mill, to experience the suffering or
      discipline necessary to bring one to a certain degree of
      knowledge or skill, or to a certain mental state.
      [1913 Webster]

WordNet (r) 3.0 (2006):

gin mill
    n 1: tavern consisting of a building with a bar and public
         rooms; often provides light meals [syn: public house,
         pub, saloon, pothouse, gin mill, taphouse]

Moby Thesaurus II by Grady Ward, 1.0:

33 Moby Thesaurus words for "gin mill":
   alehouse, bar, barrel house, barroom, beer garden, beer parlor,
   bistro, blind tiger, boozer, cabaret, cafe, cocktail,
   cocktail lounge, dive, dramshop, drinking saloon, groggery,
   grogshop, honky-tonk, local, nightclub, pothouse, pub, public,
   public house, rathskeller, rumshop, saloon, saloon bar, speakeasy,
   taproom, tavern, wine shop