unpreventable

from WordNet (r) 3.0 (2006)

unpreventable
    adj 1: not preventable; "unpreventable hysteria" [ant:
           {preventable}]

from Moby Thesaurus II by Grady Ward, 1.0

23 Moby Thesaurus words for "unpreventable":
      certain, fated, fateful, indefeasible, ineluctable, inescapable,
      inevasible, inevitable, inexorable, inflexible, irresistible,
      irrevocable, necessary, relentless, resistless, sure,
      sure as death, sure as fate, unavoidable, uncontrollable,
      undeflectable, unstoppable, unyielding