Synonym of "Ominous" is - Foreboding.

• Ominous (adjective)
English Meaning: Suggesting that something unpleasant is likely to happen:
Bangla Meaning: দুর্লক্ষণযুক্ত; অলক্ষুণে; অশুভ
Example sentence: There was an ominous silence when I asked whether my contract was going to be renewed.

Foreboding (adjective)
English Meaning: Feeling that something very bad is going to happen soon:
Bangla Meaning: আসন্ন বিপদের অনুভূতি, পূর্বানুভব।
Example sentence: There's a sense of foreboding in the capital, as if fighting might at any minute break out.

• অপশনে উল্লিখিত শব্দগুলোর অর্থ -
• Propitious (adjective)
English Meaning: Likely to result in success, or showing signs of success:
Bangla Meaning: অনুকূল; সুপ্রসন্ন; শুভ।
Example sentence: The weather was propitious for their journey.

• Auspicious (adjective)
English Meaning: Suggesting a positive and successful future:
Bangla Meaning: শুভ; অনুকূল; সুপ্রসন্ন; মাঙ্গলিক
Example sentence: They won their first match of the season 5–1 which was an auspicious start/beginning.

• Fortunate (adjective)
English Meaning: Lucky, receiving or bringing a good thing that was uncertain or unexpected.
Bangla Meaning: ভাগ্যবান; সৌভাগ্যপূর্ণ; শুভ; অনুকূল।
Example sentence: You're very fortunate to have found such a nice house.

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