Pilgrim,

You are perfectly right in your definition of "propitiation." But just for clarification, I thought I'd quote the reference from Vine's Complete Expository Dictionary of Old and New Testament Words:

Atonement (katallage, Strong's # 2643), translated "atonement" in the KJV of Rom. 5:11, signifies, not "atonement" but "reconciliation," as in the RV. See also Rom. 11:5, 2 Cor. 5:18-19.

So with the corresponding verb katallasso, see under RECONCILE. "Atonement" (The explanation of this English word as being "at-one-ment" is entirely fanciful) is frequently found in the OT. See, for instance, Leviticus, chap. 16 and 17. The corresponding NT words are hilasmos, "propitiation," 1 John 2:2, 4:10, and hilasterion, Rom. 3:25, Heb. 9:5, "mercy-seat," the covering of the ark of the covenant. These describe the means (in and through the person and work of the Lord Jesus Christ, in His death on the cross by the shedding of Hid blood in His vicarious sacrifice for sin) by which God shows mercy to sinners. See PROPITIATION.

End quote. I guess it depends on your slant of the word "Atonement." The introduction to the dictionary actually says something specific about this word, but I'll have to look it up and post it later.

(Latin phrase goes here.)