open question

noun3

1. •
   A question whose answer is not fixed by the definition of the terms contained within it.
2. •
   Synonym of open problem.
3. •
   A type of question that cannot be answered with a simple yes or no and requires a longer, more detailed response.

   • Thus an open question is one that permits a broad range of responses, while a closed question usually calls for a single-word response such as "yes" or "no" or a number. — 2001