'Covertly' definitions:

Definition of 'covertly'

(from WordNet)
adverb
In a covert manner; "he did it covertly" [ant: overtly]

Definition of 'Covertly'

From: GCIDE
  • Covertly \Cov"ert*ly\, adv. Secretly; in private; insidiously. [1913 Webster]