infidel
Concise Oxford English Dictionary © 2008 Oxford University Press:
infidel /ˈɪnfɪd(ə)l/
▶noun chiefly archaic a person who has no religion or whose religion is not that of the majority.
– origin C15: from Fr. infidèle or L. infidelis, from in- ‘not’ + fidelis ‘faithful’.
'infidel' also found in these Oxford entries:

