The Collaborative International Dictionary of English v.0.48:

Stop-gap \Stop"-gap`\, n.
   That which closes or fills up an opening or gap; hence, a
   temporary expedient.
   [1913 Webster]

         Moral prejudices are the stop-gaps of virtue. --Hare.
   [1913 Webster]

WordNet (r) 3.0 (2006):

stopgap
    n 1: something contrived to meet an urgent need or emergency
         [syn: makeshift, stopgap, make-do]

Moby Thesaurus II by Grady Ward, 1.0:

119 Moby Thesaurus words for "stopgap":
   action, ad hoc, ad hoc measure, ad lib, ad libitum, ad-lib,
   ad-libbing, alternate, alternative, answer, arrangement, artifice,
   backup, band-aid, bung, check valve, cock, contrivance, cork,
   counterfeit, countermove, coup, course of action, demarche,
   dernier ressort, device, dodge, dummy, effort, emergency,
   equivalent, ersatz, expediency, expedient, extemporaneous,
   extemporaneousness, extemporariness, extemporary, extempore,
   extemporization, fake, faucet, gimmick, imitation, impromptu,
   improvisation, improvisational, improvisatorial, improvise,
   improvised, improvision, improviso, jury-rig, jury-rigged,
   jury-rigged expedient, last expedient, last resort, last shift,
   lid, makeshift, makeshifty, maneuver, means, measure, mock, move,
   off-the-cuff, offhand, peg, phony, pin, pinch, pis aller,
   playing by ear, plug, pro tempore, provisional, proxy, recourse,
   refuge, reserve, resort, resource, rough-and-ready,
   rough-and-tumble, sea cock, secondary, shake-up, shift, solution,
   spare, spigot, spike, spile, spill, step, stop, stopper, stopple,
   stratagem, stroke, stroke of policy, substitute, tactic, tap,
   temporary, temporary arrangement, temporary expedient,
   temporary measure, tentative, token, trick, trump, unrehearsed,
   utility, valve, vicarious, working hypothesis,
   working proposition