Source : Webster's Revised Unabridged Dictionary (1913)

Deceitfully \De*ceit"ful*ly\, adv.
   With intent to deceive.

Source : WordNet®

deceitfully
     adv : in a corrupt and deceitful manner; "he acted dishonestly
           when he gave the contract to his best friend" [syn: {dishonestly},
            {venally}] [ant: {honestly}]