stiffen

If you leave the brush in the open air, the paint will dry and the bristles will stiffen.

(Chinese) 如果你把刷子放在空气中，油漆会干掉，刷毛会变硬。

His body began to stiffen with fear as he heard footsteps outside his door.

(Chinese) 当听到门外有脚步声时，他的身体因恐惧而开始变得僵硬。