1. 
[syn: astonishing, astounding, staggering, stupefying]
2.  making physically stupid or dull or insensible; 
- Example: "a stupefying blow to the head"
- Example: "the stupefying effects of hemp"
3.  shocking with surprise and consternation; 
- Example: "the stupefying impact of the tragedy"
The Collaborative International Dictionary of English v.0.48:
Stupefy \Stu"pe*fy\, v. t. [imp. & p. p. Stupefied; p. pr. &
   vb. n. Stupefying.] [F. stup['e]fier, fr. L. stupere to be
   stupefied + ficare (in comp.) to make, akin to facere. See
   Stupid, Fact, and cf. Stupefacient.] [Written also
   stupify, especially in England.]
   1. To make stupid; to make dull; to blunt the faculty of
      perception or understanding in; to deprive of sensibility;
      to make torpid.
      [1913 Webster]
            The fumes of drink discompose and stupefy the brain.
                                                  --South.
      [1913 Webster]
   2. To deprive of material mobility. [Obs.]
      [1913 Webster]
            It is not malleable; but yet is not fluent, but
            stupefied.                            --Bacon.
      [1913 Webster]
WordNet (r) 3.0 (2006):
stupefying
    adj 1: so surprisingly impressive as to stun or overwhelm; "such
           an enormous response was astonishing"; "an astounding
           achievement"; "the amount of money required was
           staggering"; "suffered a staggering defeat"; "the figure
           inside the boucle dress was stupefying" [syn:
           astonishing, astounding, staggering, stupefying]
    2: making physically stupid or dull or insensible; "a stupefying
       blow to the head"; "the stupefying effects of hemp"
    3: shocking with surprise and consternation; "the stupefying
       impact of the tragedy"
Moby Thesaurus II by Grady Ward, 1.0:
42 Moby Thesaurus words for "stupefying":
   analgesic, anesthetic, bloodcurdling, deadening, dulling,
   exceptional, extraordinary, fabulous, hair-raising, indescribable,
   ineffable, legendary, marvelous, mythical, narcotic, noteworthy,
   numbing, paralyzing, petrifying, phenomenal, portentous,
   prodigious, remarkable, stunning, stupendous, terrifying, terror,
   terror-bearing, terror-breathing, terror-breeding, terror-bringing,
   terror-fraught, terror-giving, terror-inspiring, terror-striking,
   terrorful, terroristic, unexampled, unparalleled, unprecedented,
   unspeakable, wonderful