The Collaborative International Dictionary of English v.0.48:

Resistant \Re*sist"ant\ (-ant), a. [F. r['e]sistant: cf. L.
   resistens. See Resist.]
   Making resistance; resisting. -- n. One who, or that which,
   resists. --Bp. Pearson.
   [1913 Webster]

WordNet (r) 3.0 (2006):

resistant
    adj 1: relating to or conferring immunity (to disease or
           infection) [syn: immune, resistant]
    2: able to tolerate environmental conditions or physiological
       stress; "the plant is tolerant of saltwater"; "these fish are
       quite tolerant as long as extremes of pH are avoided"; "the
       new hybrid is more resistant to drought" [syn: tolerant,
       resistant]
    3: impervious to being affected; "resistant to the effects of
       heat"; "resistant to persuasion"
    4: disposed to or engaged in defiance of established authority
       [syn: insubordinate, resistant, resistive]
    5: incapable of absorbing or mixing with; "a water-repellent
       fabric"; "plastic highly resistant to steam and water" [syn:
       repellent, resistant]

Moby Thesaurus II by Grady Ward, 1.0:

182 Moby Thesaurus words for "resistant":
   against, airtight, antagonistic, antipathetic, at odds, averse,
   ballproof, beyond control, bombproof, bony, breachy, breakaway,
   bulletproof, burglarproof, cartilaginous, cement, cemental, chewy,
   clashing, cohesive, complaining, concrete, conflicting,
   contradicting, contradictory, contumacious, coriaceous, corneous,
   corrosionproof, counteractant, counteracting, counteractive,
   countervailing, counterworking, cranky, crotchety, cursory,
   dampproof, defiant, dense, diamondlike, differing, disagreeing,
   disinclined, disobedient, disputatious, disputing, dissentient,
   dissenting, dissident, durable, dure, fibrous, fire-resisting,
   fireproof, flameproof, flintlike, flinty, foolproof, forced,
   fractious, granitelike, granitic, gristly, hard, hard as nails,
   hardhearted, hardy, hermetic, holeproof, horny, hostile, immovable,
   immune, impervious, impervious to, incorrigible, indisposed,
   indocile, indomitable, inimical, insuppressible, intractable,
   intransigent, involuntary, iron-hard, ironlike, irrepressible,
   lapideous, lasting, leakproof, leatherlike, leathery, lithoid,
   lithoidal, marble, marblelike, mutinous, noiseproof, nonconformist,
   noncooperative, nonsusceptible to disease, obdurate, objecting,
   obstinate, obstreperous, obstructive, on the barricades, opposed,
   opposing, oppositional, oppugnant, osseous, out of hand,
   perfunctory, perverse, proof, proof against, protesting,
   punctureproof, reactionary, rebellious, recalcitrant, refractory,
   reluctant, renitent, repellent, repugnant, resisting, resistive,
   restive, retardant, retardative, revolutionary, rocklike, rocky,
   ropy, rustproof, shatterproof, shedding, shellproof, shrewish,
   sinewy, solid, soundproof, steellike, steely, stiff, stonelike,
   stony, stringy, strong, stubborn, sulky, sullen, tenacious, tight,
   tough, tough as leather, unaffected, unbiddable, uncompliant,
   unconsenting, uncontrollable, uncooperative, ungovernable,
   unmalleable, unmanageable, unmoldable, unruly, unsubmissive,
   untiring, unwilling, unyielding, up in arms, vigorous, viscid,
   watertight, weatherproof, wild, wiry, withstanding