ἄτακτοςátaktos

unarranged, i.e. (by implication) insubordinate (religiously)

Greek (New Testament) · G813

Meanings

out of order, out of place (Lat. inordinatus), frequently of soldiers not keeping the ranks, or an army in disarray (cf. 3 Maccabees 1:19); hence, metaphorically, irregular, disorderly (see previous word): 1 Thessalonians 5:14.

Same root

ΑA · G1the first letter of the alphabet; figuratively, only (from its use as a numeral) the first:
τάσσωtássō · G5021to arrange in an orderly manner, i.e. assign or dispose (to a certain position or lot)
ἀτάκτωςatáktōs · G814
ἀτακτέωataktéō · G812to be (i.e. act) irregular

Where it appears

Appears 1 times in the Bible.

1 Thessalonians 5:14 Brothers and sisters, we urge you to warn those who are lazy. Encourage those who are timid. Take tender care of those who are weak. Be patient with everyone.

Source: G. Abbott-Smith, A Manual Greek Lexicon of the New Testament (1922), public domain.