sedate

Adjective

• dignified and somber in manner or character and committed to keeping promises
  • a grave God-fearing man
    
  • a quiet sedate nature
    
  • as sober as a judge
    
  • a solemn promise
    
  • the judge was solemn as he pronounced sentence
    

• characterized by dignity and propriety

Verb

• cause to be calm or quiet as by administering a sedative to
  • The patient must be sedated before the operation
    

Related words

• Synonyms: 
  grave , sober , solemn , staid , calm , tranquilize , tranquillize , tranquillise
• Antonyms: 
  stimulate , arouse , brace , energize , energise , perk up