The synonym of 'Impassive' is -

- উল্লেখিত প্রশ্নে 'Impassive' শব্দের synonym হচ্ছে Stolid.

Impassive (adjective):
English Meaning: Not showing or feeling any emotion.
Bangla Meaning: নির্বিকার; নিরাবেগ।

Synonyms: Expressionless (ভাবলেশহীন), Unexpressive (আবেগশূন্য), Unresponsive (সংবেদনহীন), Stolid (অবিচলিত), Stoic (ভাবলেশহীন)।
Antonyms: Expressive (প্রকাশক), Passionate (অনুরাগী) Alert (তৎপর), Excitable (উৎসাহী, Active (সক্রিয়)। 

Other Forms:
Impassively (adverb) - নির্বিকারভাবে।
Impassiveness, impassivity (noun) - নির্বিকারত্ব।
Example Sentence:
1. He remains utterly impassive when an entire audience is booing him behind his back.
2. She remained impassive as the officers informed her of her son's death.

Source: Website Lecture.