Conundrum (kə-nŭn’drəm) is a very difficult or insoluble problem. It can also refer to a riddle whose answer is a pun, a paradox or an enigma.
But we have heard a lot less about these debt-market disciplinarians in recent years. Instead, bond yields have been puzzlingly low, a conundrum that taxed even Alan Greenspan, the former Federal Reserve chairman. (The Economist)
Keeping employees satisfied and productive is the age-old management conundrum on which the experts rarely agree. The prestige/satisfaction link is no exception. (USA Today)