Quick Definition
ὀψάριον, ου, τό n.n. a little fish
Strong's Definition
a relish to other food (as if cooked sauce), i.e. (specially), fish (presumably salted and dried as a condiment)
Derivation: neuter of a presumed derivative of the base of G3702 (ὀπτός);
KJV Usage: fish
UBS Dictionary of the Greek New Testament
noun, n. | -ου | ὀψώνιον · παροψίς
5.16 · Foods and Condiments · Food
fish fish intended for food or the flesh of fish as food In Greek the usual meaning of ὀψάριον is a tidbit of food eaten with bread, but it occurs in later Greek in the meaning of fish, and in the NT this meaning occurs only in the fourth Gospel (compare the usage in JHN 6:9 with ἰχθύς in parallel passages).
Many languages distinguish clearly between terms for fish while still living in the water and fish which have been caught and presumably are to be used for food.
UBS Dictionary of the Greek New Testament © United Bible Societies, licensed CC BY-SA 4.0.
Thayer's Greek Lexicon
ὀψάριον, -ov, τό, (dimin. fr. ὄψον [cf. Curtius § 630] i. e. whatever is eaten with bread, esp. food boiled or roasted; hence specifically), fish: Jn. vi. 9,11; xxi. 9 sq. 13. (Comic. ap. Athen. 9, c. 35 p. 385 6. : Leian.,Geop. [οἵ Wetstein on Jn. vi. 9]; see γυναικάριον, fin. [W. 23 (22)})
Mounce Concise Greek Dictionary
ὀψάριον opsarion 5x
a little fish, Jn. 6:9, 11; 21:9, 10, 13*
Abbott-Smith Greek Lexicon
** ὀψάριον, -ου, τό
(dimin. of ὄψον, (1) cooked meat; (2) a relish or dainty, esp. fish, cf. MGr. τὸ ψάρι, fish; in comic poets and late prose writers only), [in LXX: To 2:2 א (B ὄψον)*;]
fish: Jo 6:9, 11 21:9, 10, 13.†
Moulton & Milligan — Vocabulary of the Greek NT
ὀψάριον. With the use of ὀψάριον to denote fish eaten as a titbit along with bread in Jn 6%, 219 (cf. Tob 22 5), cf. BGU IV. 109527 (A. Ὁ. 57), where after the mention of bread and pigeons we read of a λαγύνιον ταριχηροῦ (= ὧν) ὀψαρίων, ‘a jar of pickled fish”: see further P Oxy IV. 7365 (a private account—c. A.D. 1) ὀψαρί[ο]ν (ὀβολός), “sauce 1 ob.”, P Ryl IL. 22971 (a.p. 38) τοὺς ἄρτους μοι πέμψον καὶ τὸ ὀψάριον, ‘‘send me the loaves and the relish,” P Fay 1198 (c. A.D. 100) εἰς τὰ γενέσια Γεμέλλ[ης] πέμψις ὠψάρ[ι]α καὶ καὶ ἄρτον (πυροῦ ἀρτάβην) a, ‘ for Gemella’s birthday feast send some delicacies . . . and an artaba of wheaten bread,” and the late P Lond 48377 (A.D. 616) (=II. p. 328) ὀψάρια ἐκ τῶν παντοίων ὑδάτων. For the word in a more general sense cf. P Oxy III. 53178 (ii/a.D.), where a father, after bestowing good advice on his son, adds τοῖς ὀψαρίοις ἐξήλλαξας ἡμᾶς, ‘you won me over by the dainties” (Edd.). From the inscrr. we may cite OG/S 48428 (ii/a.p.) τῶν λεπτῶν ὀψαρίων, and the mention in the same document 1.2! of an ὀψαριοπώλης. The simple ὄψον (Tob 22, 78) occurs in P Hib 1. 5438 (c. B.C. 245) λάχανα mlavtlodamd καὶ ἐὰν ὄψον τι éxntls, “vegetables of all kinds, and some delicacies if you have any” (Edd.), P Tebt II. 563 (account—early i/A.D.) ἄρτων kK, ὄψον κε, and the double diminutive ὀψαρίδιον in P Oxy VII. 106778 (iii/A.D.) ἀγόρασόν pot ὀψαρίδιον ἐκ τῆς θαλάσσης (cf. Numb 117 πᾶν τὸ ὄψος τῆς θαλάσσης). The MGr ψάρι, ‘‘fish,”’ shows aphaeresis, which reveals the derivation from ψωμός, ‘morsel,’ and aw (Boisacq, pp. 737, 1076). eu For ὀψέ, ‘‘ late,” cf. P Oxy XIV. 16791 (iii/A.D.) λείαν γὰρ oat (4 ὀψέ) σοι ταῦτα ἔγραψα, ‘for I am writing this to you very late’’ (Edd.). The word is construed with a partitive gen. in such phrases as P Par 351° (B.C. 163) ὀψὲ τῆς Spas: cf. Philostratus (@f. Kayser Il. p. 171°) ὀψὲ τῶν Τρωικῶν, “Cat a late stage in the Trojan war.’’ This would support the RV rendering of Mt 28: ὀψὲ [δὲ] σαββάτων, ‘late on the sabbath day’’; but Blass now prefers ‘‘after the sabbath day,” in accordance with ὀψὲ τούτων, ‘after these things,” again from Philostratus (af. Kayser I. p. 213%), and other similar passages from late Greek: see BlassDebrunner ὃ 164. 4 and the discussion in Moulton Pro/eg. p. 72f. In P Hamb I. 2718 (B.c. 250) the writer states that he has received the yokes of oxen ‘‘late yesterday, so as to be ready to work to-day - ἐχθὲς ὀψέ, ὥστε εἰς τὴν σήμερον ἐργάζεσθαι. ᾿Οψέ is used practically as an indeclinable noun in P Lond 11778 (a.p. 113) (=III. p. 183) ἀπὸ πρωΐας » ‘
Liddell-Scott-Jones — Greek-English Lexicon
ὀψάριον (opsarion) — fish. ὀψ-άριον, τό, diminutive of ὄψον, [Refs 5th c.BC+]; λαγύνιον ταριχηροῦ (i.e. -ῶν) ὀψαρίων a jar of pickled fish, [NT+1st c.AD+]