Easton's Bible Dictionary (1897)
That by which God is rendered propitious, i.e., by which it becomes consistent with his character and government to pardon and bless the sinner. The propitiation does not procure his love or make him loving; it only renders it consistent for him to execise his love towards sinners. In Rom. 3:25 and Heb. 9:5 (A.V., “mercy-seat”) the Greek word hilasterion is used. It is the word employed by the LXX. translators in Ex. 25:17 and elsewhere as
the equivalent for the Hebrew kapporeth, which means “covering,” and is used of the lid of the ark of the covenant (Ex. 25:21; 30:6). This Greek word (hilasterion) came to denote not only the mercy-seat or lid of the ark, but also propitation or reconciliation by blood. On the great day of atonement the high priest carried the blood of the sacrifice he offered for all the people within the veil and sprinkled with it the “mercy-seat,” and
so made propitiation. In 1 John 2:2; 4:10, Christ is called the “propitiation for our sins.” Here a different Greek word is used (hilasmos). Christ is “the propitiation,” because by his becoming our substitute and assuming our obligations he expiated our guilt, covered it, by the vicarious punishment which he endured. (Comp. Heb. 2:17, where the expression “make reconciliation” of the A.V. is more correctly in the R.V. “make
propitiation.”)
Hastings' Dictionary of the Bible (1898)
PROPITIATION denotes the action of a person who in some appointed way averts the wrath aroused by some offence, and brings about a reconciliation. Thus, Christ is the "propitiation for our sins." Rom 3:25; 1 John 2:2; 1 John 4:10. The same Greek word is used by the Septuagint to denote " sin-offering," Eze 44:27 and Eze 45:19; "atonement," Num 5:8; the "mercy-seat," Heb 9:5; and the covering of the ark of the covenant. Lev 16:14.