Definition of Serious

Adjective: serious seer-ee-us

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