The Greek verb antanaplēroō is a compound of anti (in place of/on behalf of), ana (up/again), and plēroō (to fill), meaning to fill up in one's place, to complete what is lacking, or to supplement. It appears once in the New Testament (Colossians 1:24) in one of the most theologically debated verses in Paul.
Colossians 1:24 — 'I fill up in my flesh what is still lacking in regard to Christ's afflictions, for the sake of his body, which is the church' — uses antanaplēroō in a way that has generated centuries of interpretation. Paul cannot mean that Christ's atonement was incomplete (Hebrews 10:14 — 'by one sacrifice he has made perfect forever those who are being made holy'). Rather, Paul speaks of the ongoing experience of tribulation that the body of Christ endures as part of the redemptive mission — the apostle's sufferings being the continuation of the messianic suffering in the world (2 Corinthians 1:5; Philippians 3:10). His sufferings bear fruit for the church, even as they are never meritorious for salvation.