The Collaborative International Dictionary of English v.0.48:

Admissible \Ad*mis"si*ble\, a. [F. admissible, LL. admissibilis.
   See Admit.]
   Entitled to be admitted, or worthy of being admitted; that
   may be allowed or conceded; allowable; as, the supposition is
   hardly admissible. -- Ad*mis"si*ble*ness, n. --
   Ad*mis"si*bly, adv.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

154 Moby Thesaurus words for "admissible":
   OK, a propos, absolute, acceptable, ad rem, adducible, adequate,
   admissive, admissory, agreeable, all right, allowable, alright,
   appertaining, applicable, applying, apposite, appropriate, apropos,
   attestative, attestive, authentic, based on, belonging,
   better than nothing, certain, circumstantial, cogent, conclusive,
   condonable, convincing, credible, cumulative, damning, decent,
   decisive, defensible, desirable, determinative, dispensable,
   documentary, documented, eligible, enfranchised, evidential,
   evidentiary, ex parte, excusable, exemptible, expiable,
   eye-witness, factual, fair, fairish, final, firsthand, fit, fitted,
   forgivable, founded on, germane, good enough, goodish, grounded on,
   hearsay, hospitable, imbibitory, implicit, in point,
   incontrovertible, indicative, indisputable, ingestive, inoffensive,
   intromissive, intromittent, invitatory, inviting, involving,
   irrefutable, irresistible, just, justifiable, lawful, legal,
   legitimate, legitimized, licit, logical, material, moderate,
   not amiss, not bad, not half bad, not so bad, nuncupative, okay,
   open, overwhelming, pardonable, passable, permissible, pertaining,
   pertinent, plausible, presentable, presumptive, pretty good,
   probative, qualified, rational, reasonable, receivable, receptible,
   receptive, recipient, relevant, reliable, remissible, respectable,
   sanctionable, sane, satisfactory, sensible, significant, sound,
   sufficient, suggestive, suitable, sure, symptomatic, telling,
   tenable, tidy, to the point, to the purpose, tolerable,
   unexceptionable, unobjectionable, valid, venial, viable,
   vindicable, warrantable, weighty, welcoming, well-argued,
   well-founded, well-grounded, wholesome, with voice, with vote,
   workmanlike, worthy