An Infidel

is,

An Unbeliever;

"One who disbelieves the inspiration of the scriptures, or the divine institution of Christianity."
(Noah Webster's 1828)

And what concord hath Christ with Belial?
or what part hath he that believeth with an infidel?
And what agreement hath
the temple of God with idols?
for ye are the temple of the living God;
as God hath said, I will dwell in them,
and walk in them; and I will be their God,
and they shall be my people.

2 Corinthians
6:15-16