faithless
adjective uk/ˈfeɪθ.ləs/ us/ˈfeɪθ.ləs/
(NOT LOYAL)
不忠诚的;不可信赖的
not loyal and not able to be trusted
（配偶或性伴侣）不忠贞的
not faithful sexually to your marriage partner or usual sexual partner
a faithless husband 不忠的丈夫
(NOT RELIGIOUS)
无宗教信仰的
with no religious faith