conundrum /kə-nunˈdrəm/

1. A riddle, esp one whose answer is a play on words
2. Any puzzling question

• rotavirus
• rotaviruses
• ROTC
• rotch
• rotche
• rotches
• rotchie
• rote
• roted
• rotenone
• rotenones
• rotes
• rotgrass
• rotgrasses
• rotgut
• rotguts
• rother
• rother-beast
• rother-beasts
• rothers
• roti
• rotifer
• Rotifera
• rotiferal
• rotiferous