(solemn) feast (day), sacrifice, solemnity

“Feasts” From Boyd’s Bible Dictionary:

(joyful). Observed for joyous events (Gen. 21:8; 29:22; 40:20; Mark 6:21-22). Numerous religious feasts (Ex. 12:16; Lev. 23:21-24; Jude 12).

“Sacrifice” From Boyd’s Bible Dictionary:

(making sacred). Propitiatory, atoning or thanksgiving offering to God. An ordained rite (Lev. 17:4-9; Deut. 16:5-19). Sacrificial offerings numerous; but chiefly, the “burnt-offering” (Lev. 1:1-17); “sin-offering,” and “trespass-offering” (Lev. 7:1-10); “peace-offering” (Lev. 7:11-34); the latter also a “free-will” offering. These offerings could not satisfy God’s holy requirements for removing sin, but they were required of all under the law, until Christ’s sacrifice of Himself, which can and did once and for all put away sin for the believer (Heb. 9-10).

“Feasts” From Concise Bible Dictionary:

The feasts of Jehovah, as instituted under the law as given by Moses, partake more of the character of commemorations, or assemblies. of the congregation to celebrate special dealings of the Lord, and consequently special seasons—in the history of His people, being called “holy convocations.” A list of the yearly feasts is given in Leviticus 23. The first mentioned is the Sabbath, and if this is counted as one, by considering the Passover and the feast of unleavened bread as one there are seven in all—the perfect number. If the Sabbath is not included, as that was a weekly festival, being the rest of God, and on which the others were founded, then the Passover and the feast of unleavened bread may be counted as two, and still there are seven. There can be no doubt that these seven feasts were typical of the ways of blessing from the cross to the millennium. They stand thus:
Dates Lev. 23 Antitypes
The Sabbath. (Lev. 23:1-3)
Abib 14th Passover Feast. (Lev. 23:5-8) Christ our Passover is slain: “let us keep the feast,” that is of unleavened bread.
Abib 15th Feast of Unleavened Bread.
First Fruits (barley), “day after the Sabbath.” (Lev. 23:9-14) The Resurrection.
Zif. [Seven Sabbaths intervene]
Sivan. Pentecost: Feast of Weeks: First Fruits (wheat). (Lev. 23:15-22) Descent of the Holy Spirit and the Church formed.
Tammuz. Ab. Elul. [The present interval.]
Tisri 1St Feast of Trumpets. (Lev. 23:23-25) Israel awakened: they afflict their souls, receive their Messiah, and are brought into blessing in the millennium.
Tisri 10th Day of Atonement. (Lev. 23:26-32)
Tisri 15th Feast of Tabernacles: ingathering of the vintage. (Lev. 23:33-44)
These seven are called “the set feasts” (Num. 29:39; 1 Chron. 23. 31; 2 Chron. 31:3; Neh. 10:33). Also “holy convocations,” when the people assembled together to offer the various offerings, and thus be reminded of their association with the living God, to whom they owed all their blessings. To ensure this at least thrice in the year, it was enjoined that all the males should appear before the Lord three times in the year, and they must not appear empty. These times were at the Feast of Unleavened Bread (no doubt including the Passover); the Feast of Weeks, or of Harvest; and the Feast of Tabernacles, or “of Ingathering” (Ex. 23:14-17; Deut. 16:16). See PASSOVER, &c.
There are two other Feasts mentioned as yearly which were not apparently ordered of God. The 25th of Chisleu, the Feast of Dedication, instituted by Judas Maccabeus when the temple was re-dedicated after being defiled by Antiochus Epiphanes, B. C. 165 (John 10:22). The other, the Feast of Purim, on the 14th and 15th of Adar, when the Jews were delivered from the threatened destruction plotted by Haman (Esther 9:21, 26).

“Sacrifice” From Concise Bible Dictionary:

As a technical religious term “sacrifice” designates anything which, having been devoted to a holy purpose, cannot be called back. In the generality of sacrifices offered to God under the law the consciousness is supposed in the offerer that death, as God’s judgment, was on him; hence the sacrifice had to be killed that it might be accepted of God at his hand. In fact the word sacrifice often refers to the act of killing.
The first sacrifice we read of was that offered by Abel, though there is an indication of the death of victims in the fact that Adam and Eve were clothed by God with coats of skins. Doubtless in some way God had instructed man that, the penalty of the fall and of his own sin being that his life was forfeited, he could only appropriately approach God by the death of a substitute not chargeable with his offense; for it was by faith that Abel offered unto God a more excellent sacrifice than Cain (Heb. 11:4). God afterward instructed Cain that if he did not well, sin, or a sin offering, lay at the door.
The subject was more fully explained under the law: “The life of the flesh is in the blood: and I have given it to you upon the altar to make an atonement for your souls: for it is the blood that maketh an atonement for the soul” (Lev. 17:11). Not that the blood of bulls and of goats had any inherent efficacy to take away sins; but it was typical of the blood of Christ which is the witness that they have been taken away for the believer by Christ’s sacrifice.
Christ appeared once in the end of the world “to put away sin by the sacrifice of himself;” and He having once died, there remains no more sacrifice for sins (Eph. 5:2; Heb. 9:26; Heb. 10:4,12,26). Without faith in the sacrificial death of Christ there is no salvation, as is taught in Romans 3:25; Romans 4:24-25 and 1 Corinthians 15:1-4.
The Christian is exhorted to present his body a living sacrifice, holy, acceptable unto God, which is his intelligent service (Rom. 12:1; compare 2 Cor. 8:5; Phil. 4:18). He offers by Christ the sacrifice of praise to God, and even to do good and to communicate are sacrifices well pleasing to God (Heb. 13:15-16; compare 1 Pet. 2:5). For the sacrifices under the law see OFFERINGS.

Strong’s Dictionary of Hebrew Words:

Transliteration:
chag
Phonic:
khag
Meaning:
or chag {khawg}; from 2287; a festival, or a victim therefor
KJV Usage:
(solemn) feast (day), sacrifice, solemnity