infidel       
noun [ C or U ]  offensive uk/ˈɪn.fɪ.dəl/ us/ˈɪn.fə.del/
 (尤被基督徒和穆斯林用来互指)异教徒
(used especially between Christians and Muslims) someone who does not have the same religious beliefs as the person speaking
  He lived among infidels/the infidel. 他生活在异教徒中。 
 infidel armies 异教徒军队 
 Compare: atheist nounagnostic nounnon-believerunbeliever