serious minded
/ˈsɪriəs ˈmaɪndɪd/
adjective
- Having a thoughtful, earnest, and responsible attitude; not frivolous or playful.
- The serious-minded student spent every evening reviewing her notes.
- He is too serious-minded to enjoy the silly jokes his coworkers tell.
- Even as a child, she was serious-minded and preferred reading to playing games.
Antonyms