Source : Webster's Revised Unabridged Dictionary (1913)

Overwhelming \O`ver*whelm"ing\, a.
   Overpowering; irresistible. -- {O`ver*whelm"ing*ly}, adv.

Source : WordNet®

overwhelmingly
     adv : incapable of being resisted; "the candy looked
           overwhelmingly desirable to the dieting man" [syn: {overpoweringly},
            {irresistibly}]