conundrum /kə-nunˈdrəm/

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

• unimaginably
• unimaginative
• unimaginatively
• unimaginativeness
• unimagined
• unimbued
• unimmortal
• unimolecular
• unimpaired
• unimparted
• unimpassioned
• unimpeachable
• unimpeached
• unimpeded
• unimpededly
• unimplored
• unimportance
• unimportances
• unimportant
• unimportuned
• unimposed
• unimposing
• unimpregnated
• unimpressed
• unimpressible