The antonym of "quixotic" is:

The antonym of "quixotic" is: Practical.

• Quixotic (adjective)
English meaning: Having or showing ideas that are different and unusual but not practical or likely to succeed.
Bangla Meaning: উচ্চ অথচ অলীক আদর্শের অনুগামী; খামখেয়ালি; আপন স্বার্থ সম্পর্কে অসচেতন; পরোপকারী।
Example sentence: This is a vast, exciting and some say quixotic project.

• Practical (adjective)
English Meaning: Relating to experience, real situations, or actions rather than ideas or imagination
Bangla Meaning: প্রায়োগিক; ব্যবহারিক; ফলিত, ব্যবহারপটু; ব্যবহারজ্ঞ; ব্যবহারপ্রবণ; প্রয়োগবুদ্ধিসম্পন্ন; প্রয়োগপ্রবণ
Example sentence: Qualifications are important but practical experience is always a plus.

• অন্য অপশনগুলর মধ্যে -
খ) Toxic (adjective)
English Meaning: Poisonous; very unpleasant or unacceptable.
Bangla Meaning: বিষাক্ত; বিষসংক্রান্ত।
Example sentence: These substances can be toxic to humans.

গ) Idealistic (adjective)
English Meaning: Believing that very good things can be achieved, often when this does not seem likely to other people:
Bangla Meaning: ভাববাদী।
Example sentence: When I was young and idealistic I believed it was possible to change the world.

ঘ) Benevolent (adjective)
English Meaning: kind and helpful:
Bangla Meaning: দয়ালু; সদাশয়।
Example sentence: He was a benevolent old man and wouldn't hurt a fly.

Source:
1. Accessible Dictionary by Bangla Academy.
2. Cambridge Dictionary.
3. Merriam-webster Dictionary.