comes from a Greek word meaning,

A sanctified person; a holy or godly person; one who is physically pure and morally blameless or religious; one who is set apart unto God.
All believers are called saints.

Likewise the Spirit also helpeth our infirmities: for we know not what we should pray for as we ought: but the Spirit itself maketh intercession for us with groanings which cannot be uttered. And he that searcheth the hearts knoweth what is the mind of the Spirit, because he maketh intercession for the saints according to the will of God.
Romans 8:26-27

saint 1. A person sanctified; a holy or godly person; one eminent for piety and virtue. It is particularly applied to the apostles and other holy persons mentioned in Scripture...
Webster's 1828