noun
defensive perimeter; defense line
Literal military or physical defensive line. Also used figuratively for measures taken to prevent something.
敵の侵攻を防ぐために予防線を張った。
They set up a defensive perimeter to prevent the enemy's invasion.
noun
Almost always used in the phrase 予防線を張る, meaning to take precautions or lay the groundwork to avoid trouble or criticism.
See also: 予防線を張る
彼は失敗したときのために予防線を張っておいた。
He took precautions in case he failed.
上司に反論される前に予防線を張る。
I lay a safeguard before my boss can object.