(education, chiefly US) A holiday that is sometimes celebrated, usually by school students and teachers, observed on either September 28th or the last school day of September. The purpose of the holiday is to encourage students to ask more questions in the classroom.

(dated, US) Synonym of million-dollar question

If one asks a question that is stupid or to which the answer is obvious, one should not be surprised or displeased to receive a silly or bizarre response.

Alternative form of ask a silly question, get a silly answer