question mark (n.)

• catechism
• cross-question
• crux
• demand
• enigma
• feeler
• inquiry
• interrogation
• interrogative
• interrogatory
• issue
• knot
• leader
• mystery
• perplexity
• poser
• problem
• puzzle
• puzzlement
• puzzler
• query
• question
• quodlibet
• sticker
• stumper
• topic
• why