防线的英文：
defensive line
fortification

参考例句：

Secondary defense
第2防线

The enemy had to fall back on the second line of defense.
敌人不得不退到第二道防线。

Zombie Bull launches Zombie Bull Rider deep into your defenses.
僵尸牛会将牛仔僵尸甩进你的植物防线中。

The much-Publicized Siegfried Line was virtually unmanned and without guns
当初大肆吹嘘的齐格菲防线，实际上已无人也无炮防守。

Our line of defense was strongly fortified.
我们的防线壁垒森严。

Smash the enemy's defence
摧毁敌人的防线

The army pierced the enemy's line.
部队突破了敌人的防线。

Pogo Zombie hops to bypass your defenses.
跳跳僵尸能够跳过防线。

Our penetration of the enemy's defences
我军对敌人防线的突破.

The Thai players sharp passes to penetrate China's defence.
泰国队迅速撕开了中国队的防线。

defensive是什么意思：
adj. 防守的，防御的
n. 防守，防御

(in a match) the defense
守方

The defenses of the city must be strengthened.
这个城市的防御工事必须加强。

He was the then secretary of Defense.
他是当时的国防部长。

line是什么意思：
n. 线条，界线，路线；条纹；排；铁路线；生产线；台词；态度；防线；前线
v. 用线标出，划线于；使布满纹络；加衬里于；排队，排列成行

This is a lined trunk.
这是一个有衬里的箱子。

They are politically in line.
他们在政治上意见一致。

On a map there are horizontal lines and vertical lines.
在地图上有水平的线和垂直的线。

fortification是什么意思：
n. 防御工事,要塞,筑城

A minor fortification constructed beyond a main defensive position or fortification.
简易外围工事在主要防御位置或防御工事之外构筑的小防御工事

The process of planning or erecting earth fortifications.
筑墙计划或树立土制堡垒的过程

A ledge between the parapet and the moat in a fortification.
搁板在堡垒中护城河与护墙之间的搁板