The bomb must explode within less than a millionth of a second.

那枚炸弹必须在百万分之一秒内爆炸。

《柯林斯英汉双解大词典》

In order to make a nuclear explosion, the critical mass must come together within a fraction of a millionth of a second.

为促成一次核爆炸，临界质量必须在一百万分之一秒内聚集在一起。

《柯林斯英汉双解大词典》

A microsecond is a millionth of a second.

1微秒就是一百万分之一秒。

youdao

K-longs, as befits their name, live to the ripe old age of a hundred-millionth of a second.

ECONOMIST: What��s the matter?

He accomplished this by using a strobe light to freeze the action of the bullet at a millionth of a second.

CNN: A camera that can see around corners

The pulses are a mere ten-millionth of a second long.

ECONOMIST: Diamonds