A punctuation symbol (?) written at the end of a sentence or phrase to indicate a direct question.
A mark of punctuation (?) put after a sentence, word, etc. to indicate a direct question, and also used to express doubt, uncertainty, etc.; interrogation mark.
Something that is unknown, mysterious, or doubtful.
Which players will still be on the team next year remains a question mark.
An unknown factor.
In C programming, the question mark is used as a conditional symbol. For example, in the expression x1 ? x2 : x3, if x1 is not zero, then x2 is evaluated, otherwise x3 is evaluated.
Attributive form of question mark.