Quick Definition
timely, suitable
Strong's Definition
well-timed, i.e. opportune
Derivation: from G2095 (εὖ) and G2540 (καιρός);
KJV Usage: convenient, in time of need
Thayer's Greek Lexicon
εὔκαιρος, εὔκαιρον (εὖ and καιρός), seasonable, timely, opportune: βοήθεια, Heb_4:16; ἡμέρας εὐκαίρου, a convenient day, Mar_6:21. (2Ma_14:29; (Psalm 103:27 (); Sophocles O. C. 32); Theophrastus, Polybius, others.)
Mounce Concise Greek Dictionary
εὔκαιρος eukairos 2x
timely, opportune, seasonable, convenient, Mar_6:21 ; Heb_4:16
Abbott-Smith Greek Lexicon
εὔ -καιρος , -ον ,
[in LXX : Psa_104:27 ( H6256 ), 2Ma_14:29 ; 2Ma_15:20-21 , 3Ma_4:11 ; 3Ma_5:44 * ;]
timely, seasonable, suitable ( Cremer , 740): ἡμέρα , Mar_6:21 (or empty , as in Byz. and MGr .; v. MM , Exp., xiv); βοήθεια , Heb_4:16 .†
Moulton & Milligan — Vocabulary of the Greek NT
εὔκαιρος [page 262]
OGIS 762 .4 (ii/B.C.) βοηθείτω κατὰ τὸ εὔκαιρον , Michel 164 .25 ( c. B.C. 140) μερίσαι Ἀπολλωνίωι ξένιον ὅσον ἂν αὐτοῖς εὔκαιρον εἶ [ν ]αι φαίνηται . The superlative is found in P Petr II. 12 (1) .15 (B.C. 241) μεταθεῖναι τοὺς βωμοὺς ἐπὶ τοὺς εὐκαιροτάτους τόπους καὶ ἐπιφανεστάτους ἐπὶ τῶν δωμάτων , to remove the altars to the most convenient and conspicuous place on the houses (Ed.). It maybe mentioned that Pallis A Few Notes , p. 11 regards the adj. in Mk in 6 .21 γενομένης ἡμέρας εὐκαίρου , as = an empty day, a day without work, a festival; the meaning is supported from Byzantine (see Sophocles Lex. s.v. ) and modern Greek.
Liddell-Scott — Intermediate Greek Lexicon
εὔκαιρος εὔ-καιρος, ον "well-timed, in season, seasonable", Soph. : neut. εὔκαιρον "in season", Anth. :—adv. -ρως, "seasonably, opportunely", -ότερον, Plat.
STEPBible — Tyndale Abridged Greek Lexicon
εὔ-καιρος, -ον
[in LXX: Psa.104:27 (עֵת), 2Ma.14:29 2Mac 15:20-21, 3Ma.4:11 3Mac 5:44 * ;]
timely, seasonable, suitable (Cremer, 740): ἡμέρα, Mrk.6:21 (or empty, as in Byz. and MGr.; see MM, Exp., xiv); βοήθεια, Heb.4:16.†
(AS)