The Collaborative International Dictionary of English v.0.48:

Intolerable \In*tol"er*a*ble\, a. [F. intol['e]rable, L.
   intolerabilis. See In- not, and Tolerable.]
   [1913 Webster]
   1. Not tolerable; not capable of being borne or endured; not
      proper or right to be allowed; insufferable;
      insupportable; unbearable; as, intolerable pain;
      intolerable heat or cold; an intolerable burden.
      [1913 Webster]

            His insolence is more intolerable
            Than all the princes in the land beside. --Shak.
      [1913 Webster]

   4. Enormous.
      [1913 Webster]

            This intolerable deal of sack.        --Shak.
      -- In*tol"er*a*ble*ness, n. -- In*tol"er*a*bly, adv.
      [1913 Webster]

WordNet (r) 3.0 (2006):

intolerably
    adv 1: to an unacceptable degree; "The percentage of lead in our
           drinking water is unacceptably high" [syn:
           unacceptably, intolerably] [ant: acceptably, so-
           so, tolerably]

Moby Thesaurus II by Grady Ward, 1.0:

66 Moby Thesaurus words for "intolerably":
   abominably, agonizingly, awfully, baldly, balefully, bitterly,
   blatantly, brashly, confoundedly, cruelly, damnably, deadly,
   deathly, deucedly, dissatisfactorily, distressingly, dolorously,
   dreadfully, egregiously, excessively, excruciatingly, exorbitantly,
   extravagantly, flagrantly, frightfully, grievously, hellishly,
   horribly, improperly, inadequately, inadmissibly, inexcusably,
   infernally, inordinately, insufferably, insufficiently,
   insupportably, lamentably, miserably, nakedly, objectionably,
   openly, painfully, piteously, sadly, shatteringly, shockingly,
   something awful, something fierce, sorely, staggeringly, terribly,
   torturously, unacceptably, unashamedly, unbearably, unconscionably,
   undesirably, unduly, unendurably, ungratifyingly, unpardonably,
   unsatisfactorily, unsatisfyingly, unsuitably, woefully