Definitions
1.noun(grammar) A word (pronoun, pronominal adjective, or adverb) implying interrogation, or used for asking a question: why, who, when, etc.
2.nounA question; an interrogation.
3.adjective(grammar) Asking or denoting a question: as, an interrogative phrase, pronoun, or point.
4.adjectivePertaining to inquiry; questioning"He took on an interrogative tone of voice."
5.nounThe punctuation mark "?", used at the end of a sentence to indicate a question.
6.nounA state of doubt or uncertainty."There’s a question mark over whether or not he’ll be fit for the next game."
7.nounAn enigmatic, inscrutable, or mysterious person or thing; an enigma, a riddle.
8.nounPolygonia interrogationis, a North American nymphalid butterfly with a silver mark on the underside of its hindwing resembling a question mark (sense 1).