perfidiously


per·fid·i·ous

P0188700 (pər-fĭd′ē-əs)adj. Of, relating to, or marked by perfidy; treacherous. See Synonyms at faithless.
per·fid′i·ous·ly adv.
Thesaurus
Adv.1.perfidiously - in a perfidious manner; "he was playing perfidiously one side against the other"
Translations
déloyalementperfidement