question mark noun
ADJ. big, huge, serious
VERB + QUESTION MARK put His arrival clearly puts a huge question mark against the future of the present team captain.
QUESTION MARK + VERB hang over sth, remain A big question mark hangs over the wisdom of the move.
PREP. ~ against A slight question mark against her character remains. | ~ over There is now a serious question mark over his leadership ability.
You can also check other dicts: question mark (English, 中文解释 ), wordnet sense, Collins Definition