to make yourself or part of your body firm, straight and still, especially because you are angry or frightened （尤指因气愤或害怕，使浑身或身体的一部分）变僵硬，变僵直，绷紧
~ (with sth)
She stiffened with fear.
她吓呆了。
~ sth (with sth)
I stiffened my back and faced him.
我挺直了腰杆面对着他。