Quick Definition
διαβεβαιόομαι v. I assert emphatically
Strong's Definition
middle voice of a compound of 1223 and 950; to confirm thoroughly (by words), i.e. asseverate
KJV Usage: affirm constantly
UBS Dictionary of the Greek New Testament
UBS Dictionary of the Greek New Testament © United Bible Societies, licensed CC BY-SA 4.0.
Thayer's Greek Lexicon
δια-βεβαιόομαι (-οὔμαι) ; mid. to affirm strongly, assert confidently, [ef. W. 253 (238)]: περί twos (Polyb. 12, 11 (12), 6), 1 Tim. i. 7 [ef. WH. App. p. 167]; Tit. iii. 8. (Dem. p. 220, 4; Diod., Dion. Hal., Plut., Ael.)
Mounce Concise Greek Dictionary
διαβεβαιόομαι diabebaioomai 2x
to assert strongly, insist, 1 Tim. 1:7; Tit. 3:8*
Abbott-Smith Greek Lexicon
* δια-βεβαιόομαι, -οῦμαι to affirm confidently: Tit 3:8; seq. περί, I Ti 1:7 (Cremer, 140).†
Moulton & Milligan — Vocabulary of the Greek NT
διαβεβαιόομαι you about the copper” (Ed.): cf. τό. VI. goo!’ (A.D. 322) ἀλλ᾽ ἐπιδὴ μανθάνω τούτους βουλομένους ἐνεδρεύειν... τισὶ μὲν ἀπι[ο]ῦσι, ἐνίους δὲ διαβάλλοντας, ‘but whereas I learn that these persons are desirous of acting fraudulently, some by absenting themselves, and others by deception” (Edd.). Other examples are P Par 63%+ 7° (B.c. 165) ὡς διαβάλλεται, the Jewish ao/ogéa in answer to an Imperial rescript, 26 6888 & σοι alyn]Adws δια[βεβλη]μένοι προτοῦ, and BGU IV. 1040% (ii/A.b.) καθαρ[ὰ]ν yap ἔχων τὴν ψυχὴν οὐδενὸς émigt[.. . (Ἵν τῶν διαβαλόντων. In 7d. 1105" (B.C. 11) Tryphaena pleading for a divorce calls her husband 6] διαβαλλόμενος, “wohl nur ein ungeschickter Ausdruck fiir der genannte” (Ed.) = ‘‘the complained-of person.
Liddell-Scott-Jones — Greek-English Lexicon
διαβεβαιόω (diabebaioō) — to insist. διαβεβαι-όω, confirm, ὑπόληψιν [Refs 3rd c.AD+]:—usually middle διαβεβαι-όομαι, maintain strongly, affirm, confirm, [Refs 4th c.BC+]; to be positive, περί τινος [Refs 2nd c.BC+]:—passive, [Refs 1st c.BC+]