当头的英文：
head-on; right on the head

参考例句：

Tightening up management and putting strict observance above all else.
强化管理，严字当头。

May good fortune attend you!
祝你鸿运当头！

National solidarity in the face of danger
危难当头举国团结一致

The sun blazed down upon them with a crushing violence.
炎炎赤日当头灼烤着他们。

Suddenly there comes a terrible thunderclap overhead.
突然间一阵可怖的霹雳当头响了起来。

The newspaper splashed the story on page one.
那家报纸把这件事当头版新闻报导。

He knocked me on the head and blow stupefied me.
他给我当头一击,把我打得不省人事。

Suddenly Vanamee returned to himself with the abruptness of a blow
伐那米猛地清醒过来，象挨到了当头一拳似的。

Her purity smote him like a blow.It startled him
她的纯洁于他也仿佛是当头律喝，令他震惊。

She's a sponger who sucks up to people and goes down on her knees to Madam Lian for things to pawn.
"你那姑妈只会打旋磨子,给我们琏二奶奶跪着借当头"

head是什么意思：
n. 头，头部；头痛；理解力；首脑，首长
v. 作为…的首领；站在…的前头；给…加标题；出发；前进；驶往；用头顶
adj. 头的；在前头的；在顶端的；主要的；首要的

Heads will roll

a head of a gang; a ringleader; a chieftain; the head of a group; a cock
头目

They hit their heads together when heading the ball.
争顶头球时，二人的头撞在了一起。

My head is not that clear.
我的头脑不怎么清醒。

Tom headed the ball into the goal.
汤姆把球顶进了自己的球门。