The Collaborative International Dictionary of English v.0.48:

Reserve city \Reserve city\ (Banking)
   In the national banking system of the United States, any of
   certain cities in which the national banks are required (--U.
   S. Rev. Stat. sec. 5191) to keep a larger reserve (25 per
   cent) than the minimum (15 per cent) required of all other
   banks. The banks in certain of the reserve cities
   (specifically called central reserve cities) are required
   to keep their reserve on hand in cash; banks in other reserve
   cities may keep half of their reserve as deposits in these
   banks (--U. S. Rev. Stat. sec. 5195).
   [Webster 1913 Suppl.]

   In reserve, in keeping for other or future use; in store;
      as, he has large quantities of wheat in reserve; he has
      evidence or arguments in reserve.

   Reserve air. (Physiol.) Same as Supplemental air, under
      Supplemental.
      [1913 Webster]

   Syn: Reservation; retention; limitation; backwardness;
        reservedness; coldness; restraint; shyness; coyness;
        modesty.
        [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

44 Moby Thesaurus words for "in reserve":
   about to be, already in sight, approaching, aside, at hand, back,
   brewing, by, close, close at hand, coming, forthcoming, future,
   gathering, going to happen, immediate, imminent, impendent,
   impending, in anticipation, in danger imminent, in prospect,
   in readiness, in store, in the cards, in the offing, in the wind,
   in view, instant, looming, lowering, lurking, menacing, near,
   near at hand, nearing, on the horizon, overhanging, preparing,
   that will be, threatening, to come, upcoming, waiting