Quick Definition
I assert emphatically
Strong's Definition
to confirm thoroughly (by words), i.e. asseverate
Derivation: middle voice of a compound of G1223 (διά) and G950 (βεβαιόω);
KJV Usage: affirm constantly
Thayer's Greek Lexicon
διαβεβαιοομαι (διαβεβαιοῦμαι); middle to affirm strongly, assert confidently, (cf. Winer's Grammar, 253 (238)): περί τινο (Polybius 12, 11 (12), 6), 1Ti_1:7 (cf. WH's Appendix, p. 167); Tit_3:8. (Demosthenes, p. 220, 4; Diodorus, Dionysius Halicarnassus, Plutarch, Aelian)
Mounce Concise Greek Dictionary
διαβεβαιόομαι diab ebaioomai 2x
to assert strongly, insist, 1Ti_1:7 ; Tit_3:8
Abbott-Smith Greek Lexicon
* δια -βεβαιόομαι , -οῦμαι ,
to affirm confidently: Tit_3:8 ; seq . περί , 1Ti_1:7 ( Cremer , 140).†
Moulton & Milligan — Vocabulary of the Greek NT
διαβεβαιόομαι [page 147]
CPR 18 .29 (a process for inheritance A.D. 224) τοῦ δὲ Ἀφροδεισίου διαβεβαιωσαμένου , Aphrodisios having confirmed, BGU I. 19 .7 (A.D. 135) ἐπεὶ δὲ οἱ περὶ τὸν Πετεσ [ο ]ῦχον διεβεβαιώσαντο ἐκείνο [υ ]ς προτετελευτηκέναι τῆς μητρός κτλ ., ib. II. 412 .8 (iv/A.D.) διεβεβαίωσα τόδε ὡς τρίτας αὐτὴν ἀπαιτῖσθαι τῆς ποσότητος , and the late P Lond 113. 1 .21 (vi/A.D.) (= I. p. 201) διεβεβαιώσατο ἑαυτὸν τὸ τηνικαῦτα τέλειον εἶναι . See also Aristeas 99 διαβεβαιοῦμαι πάντα ἄνθρωπον προσελθόντα τῇ θεωρίᾳ τῶν προειρημένων εἰς ἔκπληξιν ἥξειν .
Liddell-Scott — Intermediate Greek Lexicon
διαβεβαιόομαι Dep. "to maintain strongly", Dem.
STEPBible — Tyndale Abridged Greek Lexicon
δια-βεβαιόομαι, -οῦμαι
to affirm confidently: Tit.3:8; before περί, 1Ti.1:7 (Cremer, 140).†
(AS)