The Collaborative International Dictionary of English v.0.48:

Provisional \Pro*vi"sion*al\, a. [Cf. F. provisionnel.]
   Of the nature of a provision; serving as a provision for the
   time being; -- used of partial or temporary arrangements; as,
   a provisional government; a provisional treaty.
   [1913 Webster]

WordNet (r) 3.0 (2006):

provisional
    adj 1: under terms not final or fully worked out or agreed upon;
           "probationary employees"; "a provisional government";
           "just a tentative schedule" [syn: probationary,
           provisional, provisionary, tentative]

Moby Thesaurus II by Grady Ward, 1.0:

112 Moby Thesaurus words for "provisional":
   accidental, ad hoc, adventitious, aleatory, alternate, alternative,
   backup, band-aid, casual, circumstantial, conditional, contingent,
   counterfeit, cut-and-try, dangerous, dependent, desultory, dummy,
   empirical, equivalent, ersatz, experimental, fake, fixed,
   forehanded, foreseeing, foresighted, forethoughted, forethoughtful,
   given, hazardous, heuristic, hit-or-miss, imitation,
   improvisational, improvised, incidental, inessential, infirm,
   insecure, insubstantial, interim, jury-rigged, makeshift,
   makeshifty, mock, nonessential, occasional, perilous, phony, pilot,
   pinch, precarious, precautional, precautionary, precautious,
   preparative, preparatory, prerequisite, pro tem, probationary,
   probative, probatory, propaedeutic, provident, proving, provisory,
   proxy, qualified, reserve, risky, rough-and-ready,
   rough-and-tumble, secondary, shaky, shifting, shifty, slippery,
   spare, specificative, specified, stated, stipulated, stipulatory,
   stopgap, substitute, temporary, tentative, test, testing, ticklish,
   token, transitional, treacherous, trial, trial-and-error, trying,
   undependable, unessential, unfaithworthy, unreliable, unsolid,
   unsound, unstable, unsteadfast, unsteady, unsubstantial, unsure,
   untrustworthy, utility, verificatory, vicarious