The word ‘saint’ comes from a root meaning “holy”. So when someone is referred to in Scripture as a saint, whether living or dead, it is generally understood to mean a holy one of God.
The Church recognizes, however, that a person’s holiness does not end in death, but is in fact perfected. Those whom the Church determines are in Heaven, through evidence of their intercession in the form of miracles, are given the title of Saint. They have finished the race, as Paul would put it, and received salvation. There is nothing unbiblical about it.