Adjective
1. 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!"2. of great consequence;
"marriage is a serious matter"3. 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"4. appealing to the mind;
"good music""a serious book"5. completely lacking in playfulness
6. requiring effort or concentration; complex and not easy to answer or solve;
"raised serious objections to the proposal""the plan has a serious flaw"