stiffen

Verb

• restrict
  • Tighten the rules
    
  • stiffen the regulations
    

• make stiff or stiffer
  • Stiffen the cream by adding gelatine
    

• become stiff or stiffer
  • He stiffened when he saw his boss enter the room
    

Related words

• Synonyms: 
  tighten , tighten up , constrain
• Antonyms: 
  loosen , loose , relax