trick question

Short definition from Wiktionary

Noun

1. 1
   A question that attempts to elicit an answer in a certain way, usually incorrectly (i.e. that seems to have an obvious answer that is however incorrect), or a question that does not have a correct answer or that hides the real question or some difficulty.
2. 2
   A complex question, whose wording hinders the ability to answer it correctly.