declare, bring (declare, show) glad (good) tidings, preach (the gospel)

“Gospel, the (εύαγγέλιον)” From Concise Bible Dictionary:

“Good news” or “glad tidings.” Everything worthy of this title must come from God. It has not always had the same character. It was good news to Adam and Eve that the Seed of the woman should bruise the head of the serpent. Doubtless they believed it, for Eve said, when Cain was born, “I have gotten a man from the Lord” (Gen. 3:15; Gen. 4:1). It was good news to Noah (when God made known that He was going to destroy all flesh) that he and his family should be saved in an ark, and that God would establish His covenant with him. Noah believed God, and was preserved (Heb. 11:7). It was good news to Abraham, when called out by God to be blessed by Him, to be told that he should have a son in his old age; that his seed should possess the land, and that in his Seed should all the nations of the earth be blessed (Gal. 3:8). Abraham believed God, and it was counted unto him for righteousness (Gen. 15:6; Rom. 4:3). It was good news to the Israelites, when slaves to Pharaoh, that God had come down to deliver them by the hand of Moses. They believed the good news, “they bowed their heads and worshipped” (Ex. 4:31). But this was only a part of the good news to Israel; they were not only to be brought out of Egypt; but to be brought into a “good land and a large, unto a land flowing with milk and honey.” Here alas, many of them failed; though this “gospel,” as it is called in the Epistle to the Hebrews, was preached to them, it did not profit them, because it was not mixed with faith in them: they “entered not in because of unbelief” (Heb. 4:2-6).
The “glad tidings of the kingdom” was prophesied of in the Old Testament and was preached by the Lord Jesus when on earth (Matt. 4:23; Luke 4:43; etc.); and will be preached in the future (Matt. 24:14). Though this gospel was rejected by Israel at large, the Lord gathered around Him a little flock, who formed the nucleus of the church at Pentecost. Then Jesus Christ was preached and the forgiveness of sins through His death, “the gospel of the grace of God,” and this was towards all mankind (Acts 20:24).
To Paul was revealed “THE GOSPEL OF THE GLORY,” that God has glorified Christ, and that His glory shines in the face of Him who put away the sins of believers (2 Cor. 4:4; 1 Tim. 1:11). So peculiarly was this committed to Paul that he called it “my gospel” (2 Tim. 2:8). It embraced more than salvation, great as that is, for he was desirous of making known “the mystery of the gospel,” which separates believers from the first man of the earth, and associates them with Christ glorified in heaven.
In the future there will be glad tidings for Israel when God’s time is come to bless them. The messengers will publish peace and salvation, and say to Zion, “Thy God reigneth” (Isa. 52:7). There will also be proclaimed THE EVERLASTING GOSPEL to the Gentiles, that which has been from the beginning, that the Seed of the woman should bruise the serpent’s head. The testimony rendered by means of angelic power is, “Fear God, and give glory to Him, for the hour of His judgment is come,” with the injunction to worship the Creator (Rev. 14:6-7).

“Preaching” From Concise Bible Dictionary:

This is often used in the New Testament for “announcing, or making known,” without the idea of preaching in a formal way, as the word is now understood. When there was persecution in the church at Jerusalem, they were all scattered, except the apostles, and they went everywhere “preaching the word” (Acts 8:1-4).
Solomon in the Ecclesiastes calls himself “the preacher,” and it is said of Noah that he was “a preacher of righteousness.” Paul was appointed a preacher (herald), and it pleased God by “the foolishness of the preaching” to save them that believe. Preaching is still used of God as the means for making known the love of God and the work of Christ.

Strong’s Dictionary of Greek Words:

Greek:
εὐαγγελίζω
Transliteration:
euaggelizo
Phonic:
yoo-ang-ghel-id’-zo
Meaning:
from 2095 and 32; to announce good news ("evangelize") especially the gospel
KJV Usage:
declare, bring (declare, show) glad (good) tidings, preach (the gospel)