poser
[noun]
Synonyms: puzzle, enigma, problem, question, riddle

[TahlilGaran] English Synonym Dictionary ▲

pos‧er /ˈpəʊzə $ ˈpoʊzər/ noun [countable] informal
[Date: 1800-1900; Language: French; Origin: poser; ⇒ pose¹]

1. British English (also po‧seur /pəʊˈzɜː $ poʊˈzɜːr/) someone who pretends to have a quality or social position they do not really have, usually in order to make people notice or admire them:
You meet a lot of posers in this job.

2. a difficult question:
That’s a real poser.

[TahlilGaran] Dictionary of Contemporary English ▲