A rhetorical question.

I can think of three answers all with different meanings : 1) a rhetorical question. - don't expect an answer 2) a moot question - the question is beyond the point 3) a controversy - the question incites two or more opposing opinions with no clear cut answer.

unsolved question

I noticed you also asked some strange question before.....

We Americans like to use simple English, a question with no answer is an un-answered question