Question

bulwark 【bulwark】n.壁垒；保垒The soldiers kept their heads down behind the bulwark.士兵们保持头低低地在堡垒的后面。

Accepted Answer

['bʊlwɜːrk] 
bulwarkan embankment built around a space for defensive purposes
A bulwark is a wall built for protection or defense. If you and your pals build a secret fort for girls only, you might want to build a bulwark to surround it — with a "No Boys Allowed" sign posted prominently.
A seawall that runs perpendicular to the shore is sometimes called a bulwark, because it defends the beach, not against invaders, but against beach erosion. Although the noun bulwark can refer to any fortified wall, it often specifically refers to an earthen wall, like a rampart. As a verb, bulwark means to fortify with a wall or to provide protection: "The volunteers used sandbags to bulwark the levee in an attempt to prevent the flooded river from overflowing its banks."
All forms of 'bulwark' will appear on average once every 1142 pages.bulwark

Front	bulwark
Pron	['bʊlwɜːrk]
Back	【bulwark】n.壁垒；保垒 The soldiers kept their heads down behind the bulwark. 士兵们保持头低低地在堡垒的后面。
Vocab	bulwarkan embankment built around a space for defensive purposes A bulwark is a wall built for protection or defense. If you and your pals build a secret fort for girls only, you might want to build a bulwark to surround it — with a "No Boys Allowed" sign posted prominently. A seawall that runs perpendicular to the shore is sometimes called a bulwark, because it defends the beach, not against invaders, but against beach erosion. Although the noun bulwark can refer to any fortified wall, it often specifically refers to an earthen wall, like a rampart. As a verb, bulwark means to fortify with a wall or to provide protection: "The volunteers used sandbags to bulwark the levee in an attempt to prevent the flooded river from overflowing its banks." All forms of 'bulwark' will appear on average once every 1142 pages. bulwark

Bulwark Built Wall Build Bʊlwɜːrk Bulwark】N.壁垒；保垒 Soldiers Heads