bulwark
n. 壁垒；保卫
For centuries the British regarded their navy as their principal bulwark against invasion.
几个世纪来，英国认为他们的海军是抵御侵略的首要防卫。
citadel
n. 城堡；要塞
The fortified city of Singapore was once considered unconquerable. In 1942, however, this citadel fell to the Japanese.
人们一度认为新加坡这个设防的城市是无法征服的，然而在一九四二年这个要塞落入日本之手。
forte
n. 专长
I am better than Jack in English but not in math;that is his forte.
我的英文比杰克强，但数学就不一样了，那是他的专长。
vigor
n. 精力，活力
The robust young pitcher performed with his usual vigor for seven innings, but he weakened in the eighth and was removed from the game.
那位强健的年轻投手以他常有的精力打完了七局，但第八局时他力气减弱而被换了下来。
invigorate
vt. 增添活力
If you feel enervated by the heat, try a swim in the cool ocean. It will invigorate you.
如果你热得感到无力，试着在凉爽的海水中游泳，它将增添你的活力。
cogent
adj. 强而有力的
Excuses for not handing work in on time vary. Some are flimsy, as, for example, "I left it at home. " Others are more cogent, such as a physician's note.
不按时交作业的理由不尽相同，有些比较薄弱，如：“我放在家里。”有些则较强而有力，例如一张医生证明。
dynamic
adj. 精力充沛的；有力的　 反：undynamic 精力不够的,
If you elect Jessica, you may be sure she will present our views forcefully and energetically. She is a very dynamic speaker.
如果选杰西卡，你能肯定她可以将我们的观点强有力的提出，因为她是一位很有力的演说者。
formidable
adj. 难以应付的
Our hopes for an easy victory sank when our opponents took the field. They were much taller and huskier, and they looked formidable.
当对手一出场，我们轻松得胜的希望就降低了，他们高壮的多，而且看起来不好对付。
impregnable
adj. 不可攻破的；坚固的
Before World War II, the French regarded their Maginot Line as an impregnable bulwark against a German invasion.
二次大战前，法国人认为他们的马其诺防线是对付德国侵略的坚固堡垒。
robust
adj. 强壮的　反：frail 虚弱的 feeble 虚弱的, 无力的
The lifeguard was in excellent physical condition. I had never seen anyone more robust.
那个救生员的身体状况良好，我不曾看过任何人比他更强壮。
tenacious
adj. 紧咬不放的；固执的
After the dog got the ball, I tried to dislodge it from her tenacious jaws, but I couldn't.
那只狗拿到球后，我试图将球从它紧咬不放的口中取下，但是却办不到。
vehement
adj. 激烈的
Your protest was too mild. If it had been more vehement, the dealer might have paid attention to it.
你的抗议太温和了，如果当时你能再激烈点，商人就会留心。