The Collaborative International Dictionary of English v.0.48:

Almighty \Al*might"y\ ([add]l*m[imac]t"[y^]), a. [AS. ealmihtig,
   [ae]lmihtig; eal (OE. al) all + mihtig mighty.]
   1. Unlimited in might; omnipotent; all-powerful;
      irresistible.
      [1913 Webster]

            I am the Almighty God.                --Gen. xvii.
                                                  1.
      [1913 Webster]

   2. Great; extreme; terrible. [Slang]
      [1913 Webster]

            Poor Aroar can not live, and can not die, -- so that
            he is in an almighty fix.             --De Quincey.
      [1913 Webster]

   The Almighty, the omnipotent God. --Rev. i. 8.
      [1913 Webster]

WordNet (r) 3.0 (2006):

almighty
    adj 1: having unlimited power [syn: almighty, all-powerful,
           omnipotent]
    n 1: terms referring to the Judeo-Christian God [syn: Godhead,
         Lord, Creator, Maker, Divine, God Almighty,
         Almighty, Jehovah]

Moby Thesaurus II by Grady Ward, 1.0:

62 Moby Thesaurus words for "almighty":
   absolute, all-knowing, all-powerful, all-seeing, all-wise, awfully,
   boundless, changeless, creating, creative, eternal,
   eternally the same, everlasting, exceedingly, glorious, good,
   hallowed, highest, holy, immortal, immutable, infinite, just,
   limitless, loving, luminous, majestic, making, merciful, mightily,
   mighty, numinous, omnipotent, omnipresent, omniscient, one,
   only too, permanent, perpetual, plenipotentiary, powerful,
   powerfully, pretty, quite, radiant, real, really, right, sacred,
   shaping, so, sovereign, supreme, terribly, terrifically, timeless,
   ubiquitous, unbounded, unchanging, undefined, unlimited, very