NOUN (1)

1. an unavoidable event;
- Example: "don't argue with the inevitable"


ADJECTIVE (2)

1. incapable of being avoided or prevented;
- Example: "the inevitable result"

2. invariably occurring or appearing;
- Example: "the inevitable changes of the seasons"

The Collaborative International Dictionary of English v.0.48:

Inevitable \In*ev"i*ta*ble\, a. [L. inevitabilis: cf. F.
   in['e]vitable. See In- not, and Evitable.]
   [1913 Webster]
   1. Not evitable; incapable of being shunned; unavoidable;
      certain. "The inevitable hour." --Gray.
      [1913 Webster]

            It was inevitable; it was necessary; it was planted
            in the nature of things.              --Burke.
      [1913 Webster]

   2. Irresistible. "Inevitable charms." --Dryden.
      [1913 Webster]

WordNet (r) 3.0 (2006):

inevitable
    adj 1: incapable of being avoided or prevented; "the inevitable
           result" [ant: avertable, avertible, avoidable,
           evitable]
    2: invariably occurring or appearing; "the inevitable changes of
       the seasons"
    n 1: an unavoidable event; "don't argue with the inevitable"

Moby Thesaurus II by Grady Ward, 1.0:

67 Moby Thesaurus words for "inevitable":
   absolute, apodictic, appointed, binding, bound, certain, clear,
   clear and distinct, clear as day, compulsory, conclusive, decided,
   decisive, definite, destined, determinate, devoted, dictated,
   doomed, fatal, fated, fateful, foredoomed, foreordained,
   imperative, in store, in the cards, indefeasible, ineluctable,
   ineludible, inescapable, inevasible, inexorable, inflexible,
   involuntary, irresistible, irrevocable, mandatory, marked,
   necessary, obligatory, ordained, perfectly sure, positive,
   predestined, predetermined, relentless, required, resistless,
   settled, sure, sure as death, sure as fate, sure-enough, true,
   unambiguous, unavoidable, uncontrollable, undeflectable,
   unequivocal, unevadable, univocal, unmistakable, unpreventable,
   unstoppable, unyielding, written