Quick Definition
σκληρύνω v. I harden
Strong's Definition
from 4642; to indurate, i.e. (figuratively) render stubborn
KJV Usage: harden
UBS Dictionary of the Greek New Testament
verb | σκληροκαρδία · σκληρός · σκληρότης · σκληροτράχηλος
88.226 · Moral and Ethical Qualities and Related Behavior · Stubbornness
to make stubborn, to make obstinate to cause to be stubborn and obstinate, especially with regard to the truth In the expression σκληρύνω τὰς καρδίας ‘to cause the hearts to be obstinate’ in HEB 3:8 HEB 3:15 HEB 4:7, καρδία must be understood as ‘the inner self’ (see 26.3) and as such the addition of καρδία merely reinforces the meaning of the verb σκληρύνω.
UBS Dictionary of the Greek New Testament © United Bible Societies, licensed CC BY-SA 4.0.
Thayer's Greek Lexicon
σκληρύνω [cf. W. 92 (88)]; 1 aor. subjune. 2 pers. plur. σκληρύνητε ; Pass., impf. ἐσκληρυνόμην ; 1 aor. ἐσκληρύνθην ; (σκληρός, 4. v-); Sept. for ΠΤ and pin, to make hard, to harden; prop. in Hippoer. and Galen; metaph. to render obstinate, stubborn, [A.V. to harden]: τινά, Ro. ix. 18 (in opp. to those who interpret it to treat harshly, ef. Fritzsche vol. ii. p. 323 sq.; [ef., too, Meyer ad loc.]); τὴν καρδίαν τινος, Heb. iii. 8, 15 and iv. 7, (fr. Ps. xciv. (xev.) 8; cf. Ex. vii. 3,22; viii. 19; 1χ. 12); pass. (Sept. for ΤῊ} and pir) to be hardened, i. e. become obstinate or stubborn: Acts xix. 9; Heb. iii. 13.
Mounce Concise Greek Dictionary
σκληρύνω sklērynō 6x
to harden; met. to harden morally, to make stubborn, Heb. 3:8, 15; 4:7; as a negation of ἐλεεῖν, to leave to stubbornness and contumacy, Rom. 9:18; mid. and pass. to put on a stubborn frame, Acts 19:9; Heb. 3:13*
Abbott-Smith Greek Lexicon
σκληρύνω
(< σκληρός), [in LXX chiefly for קשׁה hi., also for חזק ;]
to harden. Metaph., to harden, make stubborn: c. acc. pers., Ro 9:18; τ. καρδίας (Ps 94 (95):8), He 3:8, 15 4:7. Pass., to become hardened: Ac 19:9, He 3:13.†
Moulton & Milligan — Vocabulary of the Greek NT
σκληρύνω, “harden ᾿᾿ (Heb 358 a/.): cf. P Leid Xii-28 (iii/iv Α.}.) (= II. p. 209) ἕως καταμιγῇ, καὶ σκλυρην (/. σκληρυνῇ). The verb is illustrated from Hippocrates and others by Anz Subsidia, p. 342: for constr. c. articular inf. see Thackeray Gr. i. p. 54.
Liddell-Scott-Jones — Greek-English Lexicon
σκληρύνω (sklērunō) — to harden. σκληρ-ύνω, harden, opposed to μαλάσσω, [Refs 5th c.BC+]:—passive, with perfect ἐσκλήρυσμαι [Refs 5th c.BC+], to be hardened, grow hard, [Refs 4th c.BC+]
2. metaphorically, σ. τὴν καρδίαν τινός harden his heart, [LXX+NT]:—passive, [LXX]