Abbott-Smith Manual Greek Lexicon
ἄ-τακτος (G813)
1 ** ἄ-τακτος , -ον ( τάσσω ), [in LXX: III Mac 1:19 *;] out of order , out of place (Lat. inordinatus ), freq. of soldiers not keeping the ranks, or an army in disarray (cf. III Mac 1:19 ); hence, metaph., irregular , disorderly (v. previous word): I Th 5:14 .†
G. Abbott-Smith, A Manual Greek Lexicon of the New Testament (1922) — public domain