The Collaborative International Dictionary of English v.0.48:

Inalienable \In*al"ien*a*ble\, a. [Pref. in- not + alienable:
   cf. F. inali['e]nable.]
   Incapable of being alienated, surrendered, or transferred to
   another; not alienable; as, in inalienable birthright.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

35 Moby Thesaurus words for "inalienable":
   bound up in, bound up with, deep-seated, esoteric, immanent,
   impartible, implanted, implicit, incommunicable, indefeasible,
   indissoluble, indivisible, indwelling, infixed, ingrained,
   inherent, inner, inseparable, internal, intrinsic, inward,
   inwrought, irreducible, noncommunicable, noncontagious,
   noninfectious, private, resident, secret, subjective, unalienable,
   unchallengeable, undividable, unimpartable, unquestionable