猝然的英文：
abruptly; suddenly; unexpectedly

参考例句：

She accidentally swallowed the poison and death was instantaneous.
她无意中吞下毒药，猝然死去。

A sudden jarring or jerking,as from a heavy blow or an abrupt movement.
震动，摇动，颠簸(如因受重击或猝然移动而产生的)突然震动或颠簸

abruptly是什么意思：
adv. 突然地，意外地；突然地，意外地

'Good night, then,' she said abruptly.
“那么，晚安，”她生硬地说道。

At last she interrupted abruptly what he was saying.
最后她粗暴地打断了他的话。

The number of tigers has reduced abruptly in the last fifty years
在过去的五十年里，老虎的数目锐减。

suddenly是什么意思：
adv. 突然地

Suddenly the combat alert sounded.
突然战斗警报响了。

Affect suddenly with deep feeling.
因深深的感情突然打动。

twist suddenly so as to sprain.
突然的扭曲以致扭伤。

unexpectedly是什么意思：
adv. 出乎意料地，意外地

I finished work unexpectedly early.
我的工作出乎意料地提早做完。

I happened on him in the street unexpectedly.
我没想到会在大街上碰见他。

The invasion was held up by unexpectedly stout resistance.
入侵行动因遭遇到了出乎意料的顽强抵抗而受阻。