expression
in perfect order; without a hitch; flawlessly
Describes a performance, formation, or coordinated action that is executed with flawless precision, as if not a single thread is out of place. Often used for military drills, dance, or group movements.
選手たちは一糸乱れず行進した。
The athletes marched in perfect order.
ダンサーたちの動きは一糸乱れず、観客を魅了した。
The dancers' movements were flawless and captivated the audience.
From 一糸 (one thread) + 乱れず (not disordered). The image is that not even a single thread is out of place, indicating perfect order.