The antonym of the word 'Sporadic' is -

Sporadic (adjective)
English Meaning: Not happening or appearing in a pattern; not continuous or regular.
Bangla Meaning: এখানে-সেখানে বা মাঝে মাঝে ঘটে কিংবা দেখা যায় এমন; বিক্ষিপ্ত: sporadic firing.

Synonyms: Occasional (আকস্মিক), Irregular (অনিয়মিত), Intermittent (সবিরাম), spasmodic (আকস্মিক), Unsteady (টলায়মান)।
Antonyms: Frequent (প্রায়ই সংঘটিত), Regular (নিয়মিত), Steady (সুষম), Continuous (একটানা), Habitual (স্বভাবসিদ্ধ)।

Other Forms:
Sporadically (adverb) বিক্ষিপ্তভাবে।

Example Sentence:
1. Later, our contact became more sporadic but we still had occasion to work together every once in a while.
2. Sporadic cases of the disease were reported.

Source: Lecture.