Infidel.
The Greek word is apistoj, 'not believing,' and hence an 'unbeliever.' 2 Corinthians 6:15; 1 Timothy 1:5. The word is translated 'unbeliever' in Luke 12:46; 1 Corinthians 1:6; 1 Corinthians 1:14; 2 Corinthians 1:6; and 'unbelieving' in 1 Corinthians 7:14, 1 Corinthians 1:7; Titus 1:15; Revelation 21:8. Thus the scriptural use of the term does not imply the denial of the truth of Christianity, as it is now commonly understood.