ἀτακτέω -ῶ
(ἄτακτος),
primarily, of soldiers marching, to be out of order, to quit the ranks; hence, metaphorically, to be remiss, fail in the performance of duty (in π., of truancy on the part of an apprentice): 2Th.3:7 (on ἀ. and its cognates, see M, Th., 152 ff.; MM, s.vv.).†
(AS)