Antonym of the word 'Jocose' is -

• Jocose (adjective):
English Meaning: Characterized by jokes and good humor.
Bangla Meaning: (আনুষ্ঠানিরসিক; রসিকতাপূর্ণ; তামাশাপূর্ণ; হাসিখুশি।

Synonyms: Funny (মজার), Humorous (হাস্যরসাত্মক), Playful (কৌতুকপূর্ণ), Comic (হাস্যরসাত্মক), Amusing (আনন্দদায়ক)।  
Antonyms: Dull (ম্যাড়মেড়ে), Boring (বিষন্ন), Tedious (ক্লান্তিকর), Dumb (নীরব, বাকশক্তিহীন), Serious (গম্ভীর)।

Example Sentence: 
1. But behind the jocose mood was a serious determination that farmers were sticking to their protest.
2. Some moralists have classified the jocose lie as a venial sin.

Source: Lecture.