Strong's has been found to have about 15,000 errors or omissions. It is not a lexicon it does not define words it only gives the translation of the word in the KJV, right or wrong.
Here is the definition from Bauer, Danker, Arndt, Gingrich Greek Lexicon. One of if not the most highly accredited lexicons available. This represents 120-160 years of combined scholarship. Blue highlights indicates the numerous sources the scholars consulted to determine the correct definition. You will not find this is Strong's.
εὐαγγέλιον, ου, τό (s. prec. entry; Hom. et al.; LXX, TestSol D 1:13; ApcSed 14:9; Joseph., Just., Mel.) orig. ‘a reward for good news’, then simply ‘good news’ (so Plut., Sertor. 573 [11, 8]; 582 [26, 6], Phoc. 749 [16, 8]; 752 [23, 6] al.; Appian, Bell. Civ. 3, 93 §384; 4, 20 §78; Ps.-Lucian, Asin. 26; Jos., Bell. 2, 420; 4, 618; 656; IG III, 10 = II2, 1077 [OWeinreich, ARW 18, 1915, p. 43, 3]; papyrus letter [after 238 A.D.] in Dssm., LO 313f [LAE 371]=Sb 421.—Also in sacral use: Diod S 15, 74, 2 Διονύσιος τοῖς θεοῖς εὐαγγέλια θύσας=offered a sacrifice for good news to the gods; OGI 458=IPriene 105, 40f ἦρξεν δὲ τῷ κόσμῳ τῶν διʼ αὐτὸν εὐανγελίων ἡ γενέθλιος τοῦ θεοῦ [s. AHarnack, Red. u. Aufs. I2 1906, 310ff; PWendland, ZNW 5, 1904, 335ff, D. urchristl. Literaturformen 1912, 409f]; Philostrat., Vi. Apollon. 1, 28 of the appearing of Apollon.; Ael. Aristid. 53, 3 K.=55 p. 708 D.: Ζεὺς Εὐαγγέλιος) in our lit. only in the sense of good news relating to God’s action in Jesus Christ.
① God’s good news to humans, good news as proclamation
ⓐ abs.
α. τὸ εὐαγγέλιον Mk 1:15; 8:35; 10:29; Ro 1:16; 10:16; 11:28; 1 Cor 4:15; 9:18, 23; 2 Cor 8:18; Gal 2:2; Eph 3:6; Phil 1:5; 2:22; 4:3; 1 Th 2:4; 2 Ti 1:8, 10; IPhld 5:1, 2; 8:2; 9:2; ISm 5:1; 7:2; MPol 1:1; 22:1.
β. in gen., dependent on another noun ὁ λόγος τοῦ εὐ. Ac 15:7; τὸ μυστήριον τ. εὐ. Eph 6:19; cp. vs. 15; Phil 1:7, 12, 16; ἡ ἀλήθεια τοῦ εὐ. Gal 2:5, 14; Col 1:5 (but the last passage can also be transl. the true message of the gospel). ἡ ἐλπὶς τοῦ εὐ. the hope that is kindled by the gospel vs. 23; ἡ πίστις τοῦ εὐ. faith in the gospel Phil 1:27; ἐν τ. δεσμοῖς τοῦ εὐ. Phlm 13; ἡ ἐξουσία τοῦ εὐ. authority over (i.e. to proclaim) the gospel B 8:3; ἀρχὴ τοῦ εὐ. beginning (of the proclaiming) of the gospel Phil 4:15; cp. 1 Cl 47:2 (s. on this WHartke, D. Sammlung u. d. ältesten Ausgaben der Paulusbriefe 1917, 55); Mk 1:1 (s. 3 below).
γ. in certain combinations w. verbs τὸ εὐ. κηρύσσειν Mt 26:13; Mk 13:10; 14:9 (JJeremias, ZNW 44, ’53, 103–7: apocalyptic proclamation); 16:15; cp. Mt 4:23; 9:35; 24:14; Mk 1:14; Ac 1:2 D; B 5:9; GMary 463, 29; 33. καταγγέλλειν 1 Cor 9:14. γνωρίζειν 15:1. εὐαγγελίζεσθαι Gal 1:11 (cp. 2 Cor 11:7).
ⓑ in combination
α. w. adj. εὐ. αἰώνιον Rv 14:6. ἕτερον 2 Cor 11:4; Gal 1:6 (EGrässer, ZTK 66, ’69, 306–44). ἅγιον AcPlCor 2:36.
β. w. gen. (s.ivgebrauchs 1924, 45–88).
א .objective genitive εὐ. τῆς βασιλείας Mt 4:23; 9:35; 24:14. τ. θεοῦ Mk 1:14. τ. χάριτος τ. θεοῦ of God’s grace Ac 20:24. τ. εἰρήνης Eph 6:15. τ. σωτηρίας 1:13. τ. δόξης τ. Χριστοῦ of the glory of Christ 2 Cor 4:4; cp. 1 Ti 1:11 (τὸ Ἰησοῦ Χριστοῦ εὐ. Orig., C. Cels. 2, 13, 62). εὐ. τ. Χριστοῦ is usu. interpr. as the gospel (good news) about Christ (because of Ro 1:1–3; 2 Cor 4:4; 1 Th 3:2, cp. Ro 15:16) Ro 15:19; 1 Cor 9:12; 2 Cor 2:12 (here and Ro 1:1 εἰς εὐαγγέλιον=for the purpose of bringing the good news, as Appian, Bell. Civ. 4, 113 §474). 2 Cor 9:13; 10:14; Gal 1:7; Phil 1:27; 1 Th 3:2; cp. Ro 1:9; 2 Th 1:8; B 5:9; MPol 19:1. εὐ. τῆς ἀκροβυστίας the gospel for the uncircumcised Gal 2:7.
ב .Subjective genitive (τοῦ) θεοῦ Ro 1:1; 15:16; 2 Cor 11:7; 1 Th 2:2, 8, 9; 1 Pt 4:17. The one who is commissioned to do the proclaiming can be mentioned in the subj. gen. εὐ. μου, ἡμῶν Ro 2:16; 16:25; 2 Cor 4:3; 1 Th 1:5; 2 Th 2:14; 2 Ti 2:8. S. LBaudiment, ‘L’Évangile’ de St. Paul 1925; Molland (3 below) 83–97.
② details relating to the life and ministry of Jesus, good news of Jesus D 8:2; 11:3; 15:3f; 2 Cl 8:5; MPol 4:1; perh. also Mk 1:1 (LKeck, The Introduction to Mark’s Gospel, NTS 12, ’66, 352–70; DDormeyer, NTS 33, ’87, 452–68); IPhld 8:2; ISm 7:2. This usage marks a transition to
③ a book dealing with the life and teaching of Jesus, a gospel account that deals w. the life and teaching of Jesus (Just., A I, 66, 3 al.) Dg 11:6 (ἐν τοῖς εὐ.; TestSol 1:13 D; Orig., C. Cels. 1, 9, 19 [w. ἐν τοῖς προφήταις]) τὸ καθʼ Ἐβραίους εὐ.—Papias (2:17).—(Cp. ὁ τὸ εὐ. γράψας Ἰωάννης Orig., C. Cels. 5, 12, 13).—ASeeberg, D. Evangelium Christi 1905; Harnack, Entstehg. u. Entwicklg. d. Kirchenverfassung 1910, 199–239; PZondervan, Het woord ‘Evangelium’: TT 48, 1914, 187–213; MBurrows, The Origin of the Word ‘Gospel’: JBL 44, 1925, 21–33; JSchniewind, Euangelion 1; 2; 1927, ’31, Die Begriffe Wort u. Evglm. b. Pls, diss. Halle 1910; AFridrichsen, Τὸ εὐαγγέλιον hos Pls: NorTT 13, 1912, 153–70; 209–56, Der Begriff Evgl. b. Irenäus, Hippolyt, Novatian: ibid. 1917, 148–70; AOepke, D. Missionspredigt des Ap. Pls. 1920, 50ff; EBurton, ICC Gal 1921, 422f; EMolland, D. Paulin. Euangelion; D. Wort u. d. Sache ’34; RAsting, D. Verkündigung im Urchristentum ’39 (on Word of God, Gospel, Witness); GFriedrich, TW II 705–35; KRengstorf, ZNW 31, ’32, 54–56; MAlbertz, D. Botschaft des NT, vols. I and II, ’47–’57; JvDodewaard, Biblica 35, ’54, 160–73; HKoester, TU 65, ’57, 6–12; JBowman, ‘Gospel’ and Its Cognates in Palestinian Syriac, NT Essays (TManson memorial), ed. Higgins ’59, 54–67; HFrankemölle, Evangelium ’88; HKoester, From the Kerygma to the Written Gospels: NTS 35, ’89, 361–81; RAC VI 1107–60.—DELG s.v. ἄγγελος. M-M. On εὐαγγελ- terms s. New Docs 3, 12–14. EDNT. TW. Spicq. Sv.
William Arndt et al., A Greek-English Lexicon of the New Testament and Other Early Christian Literature (Chicago: University of Chicago Press, 2000), 402–403.