The Collaborative International Dictionary of English v.0.48:

Tentative \Ten*ta"tive\, a. [L. tentare to try: cf. F. tentatif.
   See Tempt.]
   Of or pertaining to a trial or trials; essaying;
   experimental. "A slow, tentative manner." --Carlyle. --
   Ten*ta"tive*ly, adv.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Tentative \Ten*ta"tive\, n. [Cf. F. tentative.]
   An essay; a trial; an experiment. --Berkley.
   [1913 Webster]

WordNet (r) 3.0 (2006):

tentative
    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]
    2: unsettled in mind or opinion; "drew a few tentative
       conclusions" [syn: doubtful, tentative]

Moby Thesaurus II by Grady Ward, 1.0:

233 Moby Thesaurus words for "tentative":
   acting, ad hoc, ad interim, alternate, alternative, ambling,
   analytic, apprehensive, awkward, backup, band-aid, blankminded,
   callow, canny, careful, cautious, circumspect, claudicant,
   counterfeit, crawling, creeping, creeping like snail, cut-and-try,
   dangerous, deliberate, demurring, desultory, determined, diffident,
   discreet, disinclined, dumb, dummy, easy, empirical, empty,
   empty-headed, equivalent, ersatz, examinational, examinatorial,
   examining, experimental, explorational, explorative, exploratory,
   fact-finding, fake, faltering, feeling, flagging, foot-dragging,
   gauche, gentle, gingerly, gradual, green, groping, guarded,
   halting, hazardous, heedful, hesitant, hesitating, heuristic,
   hit-or-miss, hobbled, hobbling, idle, ignorant, imitation,
   improvisational, improvised, inane, indagative, indecisive,
   indolent, inexperienced, infirm, innocent, insecure, inspectional,
   inspectorial, insubstantial, interim, investigational,
   investigative, investigatory, irresolute, jibbing, judicious,
   jury-rigged, know-nothing, languid, languorous, lazy,
   leaving out nothing, leisurely, limping, lumbering, makeshift,
   makeshifty, mindful, mock, moderate, naive, nescient, noncommittal,
   on guard, overlooking no possibility, pawky, perilous, phony,
   pilot, pinch, poking, poky, politic, precarious, probationary,
   probative, probatory, proving, provisional, provisory, proxy,
   prudent, raw, regardful, relaxed, reluctant, reserve, resolute,
   risky, safe, sauntering, scrupling, secondary, shaky, shifting,
   shifty, shilly-shallying, shuffling, shy, simple, slack, slippery,
   slothful, slow, slow as death, slow as molasses, slow as slow,
   slow to act, slow-crawling, slow-foot, slow-going, slow-legged,
   slow-moving, slow-paced, slow-poky, slow-running, slow-sailing,
   slow-stepped, sluggish, snail-paced, snaillike, spare, speculative,
   staggering, sticking, stickling, stopgap, straining, strange to,
   strolling, substitute, temporary, test, testing, thorough,
   ticklish, timid, toddling, token, tortoiselike, tottering,
   treacherous, trial, trial-and-error, trudging, trying, turtlelike,
   unacquainted, unadventurous, unapprized, uncertain,
   uncommunicative, uncomprehending, unconversant, undaring,
   undependable, uneasy, unenlightened, unenterprising, unfaithworthy,
   unfamiliar, unhurried, unilluminated, uninformed, uninitiated,
   unintelligent, unknowing, unposted, unprecipitate, unreliable,
   unsound, unstable, unsteadfast, unsteady, unsubstantial, unsure,
   untrustworthy, unversed, utility, vacillatory, vacuous,
   venturesome, verificatory, vicarious, waddling, willing, wobbly,
   zetetic