unserious
adjectiveUK /ʌnˈsɪəriəs/
US /ʌnˈsɪriəs/
Not thinking or acting in a careful, serious way.
He made an unserious joke during the meeting.
RELATED WORDS
OTHER MEANINGS
2. Not sincere or not meant to be taken seriously.
Her unserious apology did not convince anyone.
3. Lacking depth or importance; trivial.
They spent the afternoon in unserious conversation.
4. Not showing the seriousness expected in a formal situation.
The judge warned the lawyer about his unserious tone.