stiffen

/ˈstɪfən/
verb
  1. To become or make something rigid or less flexible.
    • Add cornstarch to the sauce to stiffen it.
    • His muscles stiffen after a long run.
    • The cold wind caused the wet clothes to stiffen on the line.
  2. To become more severe, strict, or determined.
    • The government decided to stiffen the penalties for drunk driving.
    • The company stiffened its rules about using phones during work.
    • Her resolve stiffened when she heard the news.
  3. To become tense or rigid in body posture, often due to fear or anger.
    • He stiffened when he heard a strange noise in the dark.
    • She stiffened at the insult, but said nothing.
    • The dog stiffened and growled at the stranger.
Antonyms
What does "stiffen" mean? | whatsthatwordmean | whatsthatwordmean