Expiation
The cancellation of sin. Expiation and propitiation are similar but expiation does not carry the implication of dealing with wrath, of appeasing it through a sacrifice. Generally speaking, propitiation cancels sin and deals with God's wrath. Expiation is simply the cancellation of sin. Jesus was our propitiation (1 John 2:2; 4:10 -- "atoning sacrifice" in the NIV).
