The Collaborative International Dictionary of English v.0.48:

Ineluctable \In`e*luc"ta*ble\, a. [L. ineluctabilis; pref. in-
   not + eluctabilis to be surmounted, fr. eluctari to struggle
   out of, to surmount: cf. F. in['e]luctable. See Eluctate.]
   Not to be overcome by struggling; irresistible; inescapable;
   inevitable. --Bp. Pearson.
   [1913 Webster]

         The ineluctable conditions of matter.    --Hamerton.
   [1913 Webster]

WordNet (r) 3.0 (2006):

ineluctable
    adj 1: impossible to avoid or evade:"inescapable conclusion";
           "an ineluctable destiny"; "an unavoidable accident" [syn:
           ineluctable, inescapable, unavoidable]

Moby Thesaurus II by Grady Ward, 1.0:

45 Moby Thesaurus words for "ineluctable":
   absolute, apodictic, bound, certain, clear, clear and distinct,
   clear as day, conclusive, decisive, definite, determinate, fated,
   fateful, indefeasible, ineludible, inescapable, inevasible,
   inevitable, inexorable, inflexible, irresistible, irrevocable,
   necessary, perfectly sure, positive, predestined, predetermined,
   relentless, resistless, sure, sure as death, sure as fate,
   sure-enough, true, unambiguous, unavoidable, uncontrollable,
   undeflectable, unequivocal, unevadable, univocal, unmistakable,
   unpreventable, unstoppable, unyielding