This is the definition from a Catholic dictionary:
“To placate or appease an angry person. It is one of the three fruits of every good work; the others are impetration and merit. It is also one of the four ends of the Sacrifice of the Mass, whose propitiatory power extends to sin, to satisfaction and punishment for the living, and to punishment for the dead. (Etym. Latin propitiare, to render favorable.)”
To appease or placate an angry person. That is the basic definition. In a biblical sense, Christ appeased, exhausted, bore the wrath of God, satisfying the anger of God against sin.
Please forgive me if I misunderstand your posting. It seems Catholics are still trying to appease God for your sins throgh the mass, or in other ways through the sacraments. Do you see why our theologies is worlds apart? Christ actually satsified and bore the wrath of God for those who are His. It is finished and the price has been paid in full. Therefore, we have peace with God. Romans 5.
Peace with God Through Faith
5:1 Therefore, since we have been justified by faith, we [1] have peace with God through our Lord Jesus Christ. 2 Through him we have also obtained access by faith [2] into this grace in which we stand, and we [3] rejoice [4] in hope of the glory of God. 3 More than that, we rejoice in our sufferings, knowing that suffering produces endurance, 4 and endurance produces character, and character produces hope, 5 and hope does not put us to shame, because God’s love has been poured into our hearts through the Holy Spirit who has been given to us.
6 For while we were still weak, at the right time Christ died for the ungodly. 7 For one will scarcely die for a righteous person—though perhaps for a good person one would dare even to die— 8 but God shows his love for us in that while we were still sinners, Christ died for us. 9 Since, therefore, we have now been justified by his blood, much more shall we be saved by him from the wrath of God. 10 For if while we were enemies we were reconciled to God by the death of his Son, much more, now that we are reconciled, shall we be saved by his life. 11 More than that, we also rejoice in God through our Lord Jesus Christ, through whom we have now received reconciliation.
Romans 8
God’s Everlasting Love
31 What then shall we say to these things? If God is for us, who can be [8] against us? 32 He who did not spare his own Son but gave him up for us all, how will he not also with him graciously give us all things? 33 Who shall bring any charge against God’s elect? It is God who justifies. 34 Who is to condemn? Christ Jesus is the one who died—more than that, who was raised—who is at the right hand of God, who indeed is interceding for us. [9]
Hebrews 2:17
Therefore he had to be made like his brothers in every respect, so that he might become a merciful and faithful high priest in the service of God, to make propitiation for the sins of the people.
1 John 2:2
He is the propitiation for our sins, and not for ours only but also for the sins of the whole world.
1 John 4:10
In this is love, not that we have loved God but that he loved us and sent his Son to be the propitiation for our sins.