1. (战争中的)前线，前方
The front line is the place where two opposing armies are facing each other and where fighting is going on.

2. (国家)位于战争(或冲突)前线的，与敌对国毗邻的
A front line state shares a border with a country that it is at war with or is in conflict with.

3. 处于第一线;居于极重要岗位
Someone who is in the front line has to play a very important part in defending or achieving something.

1. the line along which opposing armies face each other

Synonym: battlefrontfront