Quick Definition
ἄλογος, ον Adj unreasonable, senseless
Strong's Definition
from 1 (as a negative particle) and 3056; irrational
KJV Usage: brute, unreasonable
UBS Dictionary of the Greek New Testament
adjc. | -ον | ἀ- + λέγω
30.12 · Think · To Think, Thought
without reason, not able to reason pertaining to a lack of capacity to reason or think properly In rendering 2PE 2:12 one may translate ‘creatures unable to reason’ as ‘wild animals,’ for this is clearly the reference of the phrase ἄλογα ζῷα.
89.19 · Relations · Cause and/or Reason
unreasonable, without basis, absurd pertaining to not providing a reason or cause, in view of something being contrary to reason In some languages the equivalent of being unreasonable is being something which people should not think. Note that ἄλογος[b] refers to that which is contrary to proper reasoning, while ἄλογος[a] (30.12) pertains to a lack of capacity to reason.
UBS Dictionary of the Greek New Testament © United Bible Societies, licensed CC BY-SA 4.0.
Mounce Concise Greek Dictionary
ἄλογος alogos 3x
without speech or reason, irrational, brute, 2 Pet. 2:12; Jude 10; unreasonable, absurd, Acts 25:27*
Abbott-Smith Greek Lexicon
ἄ-λογος, -ον
[in LXX: Ex 6:12 (שָׂפָה עָרֵל), Nu 6:12 (נָפַל), Jb 11:12, Wi 11:15, 16, IV Mac3*;]
without reason, irrational: ζῷα, II Pe 2:12, Ju 10.
contrary to reason: Ac 25:27 (v. MM, VGT, s.v.).†
Moulton & Milligan — Vocabulary of the Greek NT
ἄλογος. The adverb occurs in the curious acrostic papyrus of early i/A.D., P Tebt. 11. 278%, where the story of the loss of a garment is told in short lines, beginning with the successive letters of the alphabet— ἵζητῶι Kal οὐχ εὑρίσκωι. ἧρτε ἀλόγως. (1 seek, but do not find it. It was taken without cause.’ In P Fay 192 (Hadrian’s letter) the writer asserts that his death took place oltre ἀω[ρεὶ οὔτ]ε ἀλόγως οὔτε οἰκτρῶς οὔτε ἀπίροσ]δοκήτω[ς οὔτε ἀνοήτως, the sense of “unreasonably” seems clear, ἀλόγως being emphasized by ἀνοήτως, as ἀωρεί is by ἀπροσδοκήτως. So BGU I. 74° (a.D. 167) Kal γὰρ ἂν ἄλογον εἴη κτὰλ., P Lond 973 6111. (iii/A.p.) (=III. p. 213) μὴ δόξῃς με ἀλόγῳς [- - ., P Tebt II. 4205 (iii/A.p.) ἀλόγος (1. -ws) ἐξήλθατε ἀπ’ ἐμοῦ. Later examples are P Lips I. ττ139 (iv/A.p.) and P Amh II. 145)6 (iv/v A.D.) ἐλυπήθην διότι ἀπεδήμησας ἀλόγως, “I am grieved because you went away without cause.” There is a curious use of a derived verb in P Tebt I. 138 (late ii/s.c.), where an assailant σπασάμενος ταύτην (sc. μάχαιραν) βουλόμενός pe ἀλογῆσαι κατήνεγκε [πλ]ηγαῖς τρισὶ KTA.— a rather aggressive ‘“‘neglect” or ‘‘contempt”! Cf. BGU I. 2214f. (a.p. 114) (= Selections, p. 75) ἄλογόν por ἀηδίαν συνεστήσατο, ‘picked a senseless quarrel against me,” and similarly P Ryl 11. 1445 (A.p. 38), P Lond 342° (A.p. 185) (=II. p. 174), 7. 2148 (A.D. 270-5) (ΞΞ 11. p. 161), χθὲς ἀλόγως γενόμενος εἰς ἀμπελικὸν χωρίον, “entered violently” or ‘‘without authorisation.” Similarly P Flor I. 587 (iii/A.D.) ἀλόγως ἐπελθ[όϊντες δίχα παντὸς νόμου, a “brutal” assault. We shall see a similar activity developed in καταφρονεῖν. On the other hand BGU IV. 1024-36 (iv/v A.D.) ἔδοξεν τῷ Ζ. ἄλογον εἶναι τὴν ἀξίωσιν shows the Ι sense ‘‘unreasonable.” P Grenf II. 77° (iii/iv A.D.) ἀλόγως ἀπέστητε μὴ ἄραντες [τὸ σ]ῶμα τοῦ ἀδελφοῦ ἡμῶν is not far from ‘‘unfeelingly.” Ρ Oxy III. 5264 (ii/A.p.) οὐκ ἤμην ἀπαθὴς ἀλόγως σε καταλείπιν, “50. unfeeling as to leave you without reason” (Edd.). And so on, always with a sense going decidedly beyond “‘unreasonably” and shading into “brutally.” Hence the noun use of the modern Greek ἄλογο, ‘‘horse’’; it is nearly approached in P Oxy I. 138% (early vii/A.p.), χορηγῆσαι ἄλογα εἰς τὰς γεουχικὰς χρείας, where animals in harness are meant, if not horses exclusively. Prof. Thumb remarks that as early as Dion Cassius the word = “" animal”: cf. Hatzidakis Zzz/., Ρ. 34 f. Ps 329 supplies the line of development.
Liddell-Scott-Jones — Greek-English Lexicon
ἄλογος (alogos) — unreasonable. ἄλογος, ον, without λόγος, hence,
I. speechless, [Refs 5th c.BC+]. adverb -ως without speech, [Refs 5th c.BC+] —ἄ. ἡμέρα, = Latin dies nefastus, on which no business may be done, [Refs 2nd c.AD+]
I. b lacking in eloquence, [LXX]
I.2. inexpressive, [Refs 5th c.BC+]; unutterable, ={ἄρρητος}, [Refs 5th c.BC+]
II. unreasoning, ἡδονή, ὄχλος, etc., [Refs 5th c.BC+]brutes, animals, [Refs 5th c.BC+]; especiallyin late Greek, ἄλογον, τό, = horse, [Refs 2nd c.AD+]
II.2. not according to reason, irrational, ἄ. δόξα, opposed to ἡ μετὰ λόγου δ., [Refs 5th c.BC+]; ἀλόγῳ πάθει τὴν ἄ. συνασκεῖν αἴσθησιν, instinctive feeling, in appreciating works of art, [Refs 1st c.BC+]
II.3. contrary to reason, absurd, [Refs 5th c.BC+]; unaccountable, unintelligible, [Refs 5th c.BC+]; unfit, unsuited to its end, [Refs 5th c.BC+]; groundless, [Refs 2nd c.BC+]. adverb most frequently in this sense, [Refs 5th c.BC+]: superlative -ώτατα[Refs 1st c.BC+]
III. without reckoning:
III.1. not reckoned upon, unexpected, [Refs 5th c.BC+]
III.2. not counted, null and void, ἡμέραι[LXX]
III.3. active, not having paid one's reckoning, of an ἐρανιστής, [Refs]
IV. of magnitudes, incommensurable, περὶ ἀλόγων γραμμῶν, title of work by [Refs 4th c.BC+]
IV.2. in Rhythm, irrational, of feet or syllables whose time-relations cannot be expressed by a simple ratio, χορεῖος[Refs 4th c.BC+]; ἄλογοι, i.e. συλλαβαί, [Refs 1st c.BC+]:—of the pulse, unrhythmical, [Refs 3rd c.BC+]