An Old Testament character named Nimrod sets the stage for the main definition of GIBBOR because he was the first to become one.
Cush fathered Nimrod; he was the first on earth to be a mighty-man. He was a mighty-man hunter before the LORD. Therefore it is said, “Like Nimrod a mighty-man hunter before the LORD.” Gen. 10:8
The Lord will go forth like a mighty-man…Isa. 42:13
But the LORD is with me as a dread warrior;
therefore my persecutors will stumble;
they will not overcome me.
For to us a child is born,
to us a son is given;
and the government shall be upon his shoulder,
and his name shall be called
Wonderful Counselor, Mighty(גִּבּוֹר) God,
Everlasting Father, Prince of Peace.
He feared greatly, because Gibeon was a great city, like one of the royal cities, and because it was greater than Ai, and all its men were warriors.
גִּבּוֹר, גִּבֹּר adj. [root גָּבַר].—(1) strong, mighty, impetuous, used of a hunter, Gen. 10:9; commonly of an impetuous soldier, a hero, 2 Sa. 17:10; Ps. 33:16; 45:4; מֶלֶךְ גִּבּוֹר “a mighty king” (Alexander the Great), Dan. 11:3. אֵל גִּבּוֹר a mighty hero. [The mighty God: Christ is spoken of.] Isa. 9:5; 10:21; comp. Eze. 32:11. Gen. 6:4, הֵמָּה הַגִּבֹּרִים אֲשֶׁר מֵעוֹלָם אַנְשֵׁי הַשֵּׁם “these are the heroes, those who were famous of old;” Pro. 30:30, “the lion is a hero among beasts;” also used of a soldier generally, Jer. 51:30; Ps. 120:4; 127:4; גִּבּוֹר חַיִל “a mighty warrior,” Jud. 6:12; 11:1; 1 Sa. 9:1; pl. גִּבֹּוִרֵי חַיִל 2 Ki. 15:20; and גִּבּוֹרֵי חֲיָלִים 1 Ch. 7:5; 11:40. Used of God, Ps. 24:8, יְהֹוָה עִזּוּז וְגִבּוֹר יְהֹוָה גִּבּוֹר מִלְחָמָה “Jehovah (is) strong and mighty, Jehovah (is) mighty in battle.” Deu. 10:17; Jer. 32:18; Neh. 9:32. In mockery, Isa. 5:22, הוֹי גִּבּוֹרִים לִשְׁתּוֹת יָיִ֑ן אַנְשֵׁי־חַיִל לִמְסֹךְ שֵׁכָר “woe to those who are heroes in drinking wine, who are mighty in mingling strong drink.”
Gesenius, W., & Tregelles, S. P. (2003). Gesenius’ Hebrew and Chaldee lexicon to the Old Testament Scriptures (153).