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. (1 John 4:10 ESV)The English word propitiation is a funny-sounding one but it is rich in theological content. It is from the Greek, ἱλασμός (hilasmos), and it means an expiation, an appeasement. Noah Webster defines expiation in part as
The act of atoning for a crime; the act of making satisfaction for an offense,by which the guilt is done away, and the obligation of the offended person to punish the crime is canceled; atonement; satisfaction.It is similar to another word rendered propitiation from the Greek:
...for all [Jews and Gentiles] have sinned and fall short of the glory of God, and are justified by his grace as a gift, through the redemption that is in Christ Jesus, whom God put forward as a propitiation by his blood, to be received by faith. (Romans 3:23-25a ESV)
Here propitiation comes from ἱλαστήριον (hilastērion), which Thayer defines as:
1) relating to an appeasing or expiating, having placating or expiating force, expiatory; a means of appeasing or expiating, a propitiationPulling the terms together, one finds in the New Testament that Christ is the sacrificial victim slain to appease (to turn aside) the wrath of a holy and just God offended at sin. In other words, Christ satisfied the Divine Judgment by taking the wrath of God against sin by dying on the cross and, in this way, a human sinner can go unpunished and be forgiven. We who trust in Christ do not receive the punishment our sins deserve because Christ stood in our stead and bore the wrath that God's justice demands. A Christian cannot be punished for that which has been forgiven through the atonement of Christ!
1a) used of the cover of the ark of the covenant in the Holy of Holies, which was sprinkled with the blood of the expiatory victim on the annual day of atonement (this rite signifying that the life of the people, the loss of which they had merited by their sins, was offered to God in the blood as the life of the victim, and that God by this ceremony was appeased and their sins expiated); hence the lid of expiation, the propitiatory
1b) an expiatory sacrifice
1c) a expiatory victim