The Roman Catholic Church uses the term "Saint" to refer to a special tier of believer, above and beyond a standard Christian. This hijacks the Biblical meaning of the word, and attacks important doctrines regarding the "ordinary" believer's status before God.
The Catholic Church establishes a criteria for who may be declared a "Saint":
The above criteria has no Biblical basis - therefore it is self-refuting. This little list is found or hinted at nowhere in the Word of God. It's the invention of mankind, and God does not honor it.
A "saint" is "one who is sanctified" (1 Corinthians 1:2). To be "sanctified" is "to be made holy", as our English word "saint" comes from the Latin word "sanctus", meaning "holy".
It is the most common term used to refer to all believers in the entire Bible. It never represents or implies some special category of believers who have performed at least 2 miracles.
Psalm 30:4
4 Sing unto the Lord, O ye saints of his, and give thanks at the remembrance of his holiness.
Psalm 34:9
9 O fear the Lord, ye his saints: for there is no want to them that fear him.
Furthermore, "saint" is used dozens of times in Scripture to refer to those still living. The term applies to living people over 80% of the time that it's used:
Philippians 4:21-22
21 Salute every saint in Christ Jesus. The brethren which are with me greet you.
22 All the saints salute you, chiefly they that are of Caesar's household.
I implore you to quickly scroll through this Bible search query for "saint" on Bible Gateway so that you can see for yourself the dozens of times it is used to refer to plain, ordinary, living believers. Listing every one of the scores of verses here would get redundant.
Every believer in Jesus Christ, regardless of their lifestyle, or whether they performed 2 miracles, is a "saint", because every believer is eternally sanctified on the basis of their faith:
Acts 26:17-18
17 Delivering thee from the people, and from the Gentiles, unto whom now I send thee,
18 To open their eyes, and to turn them from darkness to light, and from the power of Satan unto God, that they may receive forgiveness of sins, and inheritance among them which are sanctified by faith that is in me.
This is because the righteousness of God is given to us when we believe (Romans 4:5). We are sanctified because the payment of Jesus Christ on the cross has atoned for every last one of our sins:
Hebrews 10:10-14
10 By the which will we are sanctified through the offering of the body of Jesus Christ once for all.
11 And every priest standeth daily ministering and offering oftentimes the same sacrifices, which can never take away sins:
12 But this man, after he had offered one sacrifice for sins for ever, sat down on the right hand of God;
13 From henceforth expecting till his enemies be made his footstool.
14 For by one offering he hath perfected for ever them that are sanctified.
From above, note:
Therefore once someone is a saint, they are always a saint, as such are sanctified and perfected "for ever".
I hope you grasp the implications of Hebrews 10:14. It means that in the over 50 mentions of the word "saint" to refer to living people, we are being told that those people will go to Heaven because they are perfected forever. And many times, as in Psalms, it's a term directed towards entire congregations of vast amounts of people.
This fantastic proof for Eternal Security is lost when the term is hijacked and used to only refer to a special tier of dead believers.
From the above verses, we gather that in one sense, a believer is eternally sanctified the moment that they believe in Jesus. This can therefore be called "eternal sanctification", or sometimes it's also called "judicial sanctification".
It's also important to mention, though, that there is another sense in which sanctification is referred to in the Bible that has to do with the way you live. There are various terms for this, such as "temporal (meaning 'in-time') sanctification", "fellowship sanctification", "experiential sanctification", and so on.
This sense refers to a believer, who is already eternally sanctified, living a holy life and walking in the spirit of the new nature. For example:
1 Corinthians 7:14
14 For the unbelieving husband is sanctified by the wife, and the unbelieving wife is sanctified by the husband: else were your children unclean; but now are they holy.
This experiential, temporal sanctification has no effect whatsoever on your eternal sanctification as a believer, because as was already shown, that eternal sanctification is based solely on the work of Jesus Christ and faith in Him, and had nothing to do with your works or life to start with.
It's easy to tell which sense sanctification is being used by the context - if it has to do with living a certain way, that's temporal sanctification. If, on the other hand, the context is the payment or work of Jesus Christ, it's referring to eternal, judicial sanctification - when you were declared "not-guilty", and given the righteousness of God Himself (Philippians 3:9) when you believed in Jesus.
The Roman Catholic Church's false concept of a saint only has to do with a person's personal piety and supposed miraculous intercession. The Bible's absolute concept of a saint has to do with the fact that we are made holy forever by faith in the Holy One and His sacrifice, and justified before God on that basis alone (Romans 3:28, 8:30).