The Collaborative International Dictionary of English v.0.48:

Stupendous \Stu*pen"dous\, a. [L. stupendus astonishing, p.
   future pass. of stupere to be astonished at. Cf. Stupid.]
   Astonishing; wonderful; amazing; especially, astonishing in
   magnitude or elevation; as, a stupendous pile. "A stupendous
   sum." --Macaulay.
   [1913 Webster]

         All are but parts of one stupendous whole. --Pope.
   [1913 Webster] -- Stu*pen"dous*ly, adv. --
   Stu*pen"dous*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

stupendously
    adv 1: to a stupendous degree; "stupendously ignorant people"