Which of the following best describes the meaning of the word "Ephemeral"?

The correct answer, is Something that is temporary or short-lived.

Ephemeral (adjective): 
English Meaning: Lasting for only a short time.
Bangla Meaning: স্বল্পজীবী; স্বল্পস্থায়ী।

Synonyms: Transient (স্বল্পস্থায়ী; ক্ষণস্থায়ী), Fleeting (ক্ষণিকের; ক্ষণকালীন), Momentary (ক্ষণিক), Brief (অস্থায়ী, সংক্ষিপ্ত), Fugitive (দ্রুত ধাবমান)। 
Antonyms: Long-lived (দীর্ঘজীবী), Permanent (স্থায়ী; চিরস্থায়ী), Endless (অন্তহীন), Eternal (অনন্ত), Immortal (অমর), Lasting (স্থায়ী)। 

Other Forms: Ephemerally (adverb).

Example Sentence: 
1. Happiness for Aristotle is not a fleeting feeling or an ephemeral passion.
2. the autumnal blaze of colors is always to be treasured, all the more so because it is so ephemeral.

Source: Website lecture.