Adverb
1. faithlessly
Adjective
1. traitorously, treacherously, treasonably, false
2. mendacious, specious, trumped-up, untrue, wrong, dishonest, dishonorable, counterfeit, imitative, incorrect, wrong, insincere, mistaken
3. incorrect, invalid
4. hollow
5. insincere, delusive
6. unrealistic, fake
7. faux, imitation, simulated, artificial, unreal, dishonest
8. dishonorable, off-key
9. sour, inharmonious, unharmonious, assumed
10. fictitious, fictive, pretended, put on, sham, counterfeit, imitative, untrue
10. inconstant