serious

Adjective

• requiring effort or concentration; complex and not easy to answer or solve
  • raised serious objections to the proposal
    
  • the plan has a serious flaw
    

• completely lacking in playfulness

• appealing to the mind
  • good music
    
  • a serious book
    

• causing fear or anxiety by threatening great harm
  • a dangerous operation
    
  • a grave situation
    
  • a grave illness
    
  • grievous bodily harm
    
  • a serious wound
    
  • a serious turn of events
    
  • a severe case of pneumonia
    
  • a life-threatening disease
    

• of great consequence
  • marriage is a serious matter
    

• concerned with work or important matters rather than play or trivialities
  • a serious student of history
    
  • a serious attempt to learn to ski
    
  • gave me a serious look
    
  • a serious young man
    
  • are you serious or joking?
    
  • Don't be so serious!
    

Related words

• Synonyms: 
  unplayful , sober , good , dangerous , grave , grievous , severe , life-threatening
• Antonyms: 
  playful , frivolous