Atakteo (ἀτακτέω) means "to be disorderly," "to act out of rank," "to behave improperly" — specifically to abandon one's assigned post or responsibility. A military term from a-taxis (disorder, out of rank), it appears once in 2 Thessalonians 3:7, where Paul says he and his team "did not live among you in a disorderly way." The noun and adjective forms (ataktos, G813; ataktos, G814) also appear in the same passage and in 1 Thessalonians 5:14.
The Thessalonians' disorder was specific: some had stopped working, apparently believing the Second Coming was so imminent that labor was pointless. Paul's counter-model is striking: "We worked night and day, laboring and toiling so that we would not be a burden to any of you" (2 Thessalonians 3:8). His rule: "If anyone is not willing to work, let him not eat" (3:10). Proper anticipation of Christ's return increases diligence, not idleness. The military metaphor is intentional: soldiers don't abandon their posts because the general is coming; they hold them because he is coming. Faithful stewardship of daily responsibility — work, family, community — is the posture of those who genuinely believe the Lord is near.