M. F. Sadler discusses the meaning of “saint” in his 1876 book, The Second Adam and the New Birth:
The word “saint,” or “holy person,” is now almost universally used as implying real purity of heart and devotion to God’s service. It is applied to Apostles, such as St. Peter or St. Paul; to eminent men who have been raised up by God in bygone times to contend for the faith, such as St. Athanasius or St. Augustine; or to men and women of very deep holiness and spirituality of mind.
In the New Testament, on the contrary, it is the common appellation of Christians. In no one place is it used to distinguish Christians of very deep holiness and spirituality from those who have not attained to such a measure of conformity to God’s will. In only a small number of texts does it imply internal purity and spirituality, and in these places it has reference not to the present character of Christians, but to that which those will be found to possess at Christ’s second coming who have continued in that service of Christ to which at Baptism they were solemnly separated and set apart. (111)
As James Jordan often says, the meaning of saint is to have sanctuary access:
[God] raised us up with him and seated us with him in the heavenly places in Christ Jesus (Ephesians 2:6 ESV)
Let us then with confidence draw near to the throne of grace, that we may receive mercy and find grace to help in time of need. (Hebrews 4:16 ESV)