The Collaborative International Dictionary of English v.0.48:

Suitable \Suit"a*ble\, a.
   Capable of suiting; fitting; accordant; proper; becoming;
   agreeable; adapted; as, ornaments suitable to one's station;
   language suitable for the subject. -- Suit"a*ble*ness, n.
   -- Suit"a*bly, adv.
   [1913 Webster]

   Syn: Proper; fitting; becoming; accordant; agreeable;
        competent; correspondent; compatible; consonant;
        congruous; consistent.
        [1913 Webster]

WordNet (r) 3.0 (2006):

suitable
    adj 1: meant or adapted for an occasion or use; "a tractor
           suitable (or fit) for heavy duty"; "not an appropriate
           (or fit) time for flippancy" [syn: suitable, suited]
    2: worthy of being chosen especially as a spouse; "the parents
       found the girl suitable for their son" [syn: desirable,
       suitable, worthy]

Moby Thesaurus II by Grady Ward, 1.0:

111 Moby Thesaurus words for "suitable":
   a propos, acceptable, according to Hoyle, ad rem, adapted,
   adequate, admissible, advantageous, advisable, ample, applicable,
   apposite, appropriate, apropos, apt, auspicious, barely sufficient,
   becoming, befitting, civil, commensurate, competent, condign,
   congruous, convenient, correct, corresponding, decent, decorous,
   deserved, desirable, dovetailing, due, eligible, enfranchised,
   enough, equal to, expedient, favorable, feasible, felicitous, fit,
   fitted, fitten, fitting, fortunate, fructuous, geared, genteel,
   good, good enough, happy, just, just right, kosher, likely, lucky,
   meet, merited, meshing, minimal, minimum, nice, normal, normative,
   on the button, opportune, pat, plenty, plenty good enough, politic,
   presentable, profitable, proper, propitious, proportionate,
   providential, qualified, reasonable, recommendable, relevant,
   requisite, right, right and proper, righteous, rightful, ripe,
   satisfactory, seasonable, seemly, sortable, substantial,
   sufficient, sufficient for, sufficing, suited, suiting, tailored,
   timely, to be desired, to the point, to the purpose, up to, urbane,
   useful, well-timed, wise, with voice, with vote, worthwhile,
   worthy