noun / verb
riddle
RID-ul/ˈrɪdl/
A question or problem that takes clever thinking to solve.
The friends work on a riddle about keys that open no locks.

Etymology
Old English rædels already meant a riddle, alongside counsel, conjecture, and discussion. The modern word preserves the puzzling-question sense within that older range of meanings.
In context
There is a riddle that is so counterintuitive, it still seems wrong even if you know the answer.
More examples
- We solved the riddle after several hints.
- The missing key remained a riddle to everyone.
- He enjoyed riddling his friends with puzzling questions.
Forms
riddle · riddles · riddled · riddling