挡箭牌的英文：
pretext; shield

参考例句：

He now regards these scruffy photographs as his shield and buckler
他现在把这些一文不值的照片当成他的护身符和挡箭牌。

Something intended to conceal the true nature,especially of an activity;a subterfuge.
挡箭牌企图掩盖本质，尤指某活动的真实性质的事物;狡猾的逃避手段

pretext是什么意思：
n. 借口，托辞
v. 以…为借口

There is no sense in fastening on that pretext of yours.
一味强调你那个借口是没有用处的。

Negotiating in bad faith under the pretext of concluding a contract.
假借订立合同，恶意进行磋商。

He remained home on the pretext of being sick.
他以生病为借口留在家里。

The tyrant will always find a pretext for his tyranny.
暴君总有他暴行的借口。

He pretexted an early engagement in town the next morning.
他借口明天早晨在城里有约会。

shield是什么意思：
n. 盾；保护人；防护物
v. 保护；庇护；包庇；挡开

concrete for radioactive ray shielding
放射线屏蔽用混凝土

God is our shield.
神是我们的保护者。

It could then have served as a trusty shield.
它就可以成为一个可靠的屏障。

The sword glanced off the shield.
剑擦过盾牌。

Riot shield (shield for use by police or soldiers dealing with riots )
防暴盾牌(警察或士兵对付暴乱用的).