I stiffened my back and faced him.

我挺直了腰杆面对着他。

She stiffened with fear.

她吓呆了。

Ada stiffened at the sound of his voice.

听到他的声音，艾达僵住了。

My muscles had stiffened up after the climb.

爬上去以后我两腿都发僵了。

He leaned towards her and she stiffened at this invasion of her personal space.

他向她俯过身去，这种侵犯她个人空间的举动让她绷紧了身子。