WordWeb Online

1. Of great consequence
   "marriage is a serious matter"
    
2. 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!"
    
3. Causing fear or anxiety by threatening great harm
   "a serious wound";
   - dangerous, grave, grievous, severe, life-threatening
    
4. Appealing to the mind
   "a serious book";
   - good
    
5. Requiring effort or concentration; complex and not easy to answer or solve
   "raised serious objections to the proposal"; "the plan has a serious flaw"
    
6. Completely lacking in playfulness
   - unplayful, sober

See also: critical, difficult, earnest, earnestness, fun, grave, hard, important, intellectual, of import, overserious, playfulness, real, sedate, serious-minded, serious-mindedness, seriousness, sincere, sincerity, sober, sobering, solemn, solid, thoughtful

Antonym: frivolous

Encyclopedia: Serious