Quick Definition
I have strength for, am perfectly able
Strong's Definition
to have full strength, i.e. be entirely competent
Derivation: from G1537 (ἐκ) and G2480 (ἰσχύω);
KJV Usage: be able
Thayer's Greek Lexicon
ἐξισχύω: 1 aorist subjunctive 2 person plural ἐξισχύσητε, to be eminently able, to have full strength (cf. ἐκ, VI. 6) followed by an infinitive Eph_3:18. (Sir_7:6; rare in Greek writings, as Dioscor., Strabo, Plutarch.)
Mounce Concise Greek Dictionary
ἐξισχύω exischuō 1x
to be fully able, be strong, Eph_3:18
Abbott-Smith Greek Lexicon
**† ἐξ -ισχύω ,
[in LXX : Sir_7:6 * ;]
to have strength enough, to be quite able: c . inf ., Eph_3:18 .†
Moulton & Milligan — Vocabulary of the Greek NT
ἐξισχύω [page 224]
BGU I. 275 .11 (A.D. 215) καὶ ἐπείρασαν αὐτὴν ( sc. μηχανὴν ) ἐπανοῖξαι καὶ οὐκ ἐξείσχυ̣σαν̣, P Oxy VIII. 1120 .7 (early iii/A.D.) ἀλλὰ οὗτος ἐξείσχυσεν τὰ βιβλείδια ἀθετηθῆναι , but his influence procured the rejection of the petition. See also Vett. Val. p. 288 .12 πολλάκις γὰρ ὑπ᾽ ὄψιν προδείξαντες τὸ ἀποτέλεσμα ἠτόνησαν διὰ τὸ ἐπὶ δυναστικοῦ τόπου ἕτερον τετευχότα ἐξισχῦσαι . These examples make it at least doubtful whether it is possible to give the verb the intensive meaning be fully able, be strong (RV), often assigned to it in Eph_3:18 .
Liddell-Scott — Intermediate Greek Lexicon
ἐξισχύω fut. ύσω "to have strength enough, to be quite able" to do, c. inf., NTest.
STEPBible — Tyndale Abridged Greek Lexicon
ἐξ-ισχύω
[in LXX: Sir.7:6 * ;]
to have strength enough, to be quite able: with inf., Eph.3:18.†
(AS)
📖 In-Depth Word Study
Be able (1840) exischuo
May be able (1840) (exischuo from ek = an intensifies + ischuo = to be strong, able - see related word ischus) means to be eminently able, to have strength enough, to be quite able to do, to be in full strength, to be fully able. This compound word is one of the strongest Greek words for strength and signifies one completely capable of doing or experiencing something.
In the English rendering it is easy to pass over the may be able which is brought out more graphically in other translations like the Amplified which renders it...
That you may have the power and be strong to apprehend and grasp
The point is that the preface asking for power to grasp implies that divine enabling is essential. It conveys the ability to attain an objective, in this case to lay hold of.
Vincent writes that exischuo
occurs only here. The preposition ex has the force of fully or eminently. Ischus is strength embodied; inhering in organized power. Hence it is an advance on dunamei or might in Eph 3:16. Paul prays that the inward might or virtue may issue in ability to grasp. Compare Lu 14:30; 16:3; Acts 27:16; Jas. 5:16, and see notes.