ENIGMA (Gr. aTvcyµa)  , a riddle or puzzle, especially a form of verse or prose composition in which the answer is concealed by means of metaphors . Such were the famous riddle of the Sphinx and the riddling answers of the ancient oracles . The composition of enigmas was a favourite amusement in Greece and prizes were often given at banquets for the best solution of them (Athen. x . 457) . In France during the 17th century enigma-making became fashionable . Boileau, Charles Riviere Dufresny and J . J . Rousseau did not consider it beneath their literary dignity . In 1646 the abbe Charles Cotier (1604—1682) published a Recueil des enigmes de ce temps . The word is applied figuratively to anything inexplicable or difficult of understanding .