The word 'Onerous' means -

♦ Onerous (adjective)
English Meaning: Difficult to do or needing a lot of effort.
Bangla Meaning: কষ্টসাধ্য; গুরুভার: onerous duties.

Synonyms: Inconvenient (অসুবিধাজনক), Troublesome (বিরক্তিজনক), Hard (কষ্টকর), Cruel (যন্ত্রনাদায়ক), Rough (রুক্ষ্ম)।
Antonyms: Easy (সহজ), Effortless (উদ্যমহীন), Soft (মসৃন), Comforting (আরামদায়ক), Restful (শান্তিপূর্ন)।

Other Forms:
- Onerously (adverb).

Example Sentence: 
1. The new rules will place onerous responsibilities on employers.
2. The government imposed onerous taxes on imports.

Options,
- Forestall: To prevent something from happening by acting first.
- Sporadic: Not happening or appearing in a pattern.
- Abstemious: Not self-indulgent, especially when eating and drinking.

Source: Website Lecture.