Synonyms of 'conundrum'
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If you describe something or someone as an enigma, you mean they are mysterious or difficult to understand.
This country remains an enigma for the outside world.
A poser is a difficult problem or puzzle.
Here's a little poser for you.
Thesaurus for conundrum from the Collins English Thesaurus
A conundrum is a problem or puzzle which is difficult or impossible to solve .