01 To ponder or study over some perplexing problem or matter. Puzzle, riddle, enigma refer to something baffling or confusing, which is to be solved. A puzzle is a question or problem, intricate enough to be perplexing to the mind. It is sometimes a contrivance made purposely perplexing to test your ingenuity.
03 Enigma refers to some baffling problem with connotations of mysteriousness. Puzzle suggests mental embarrassment amid a complexity of possible decisions. “I cannot forecast to you the action of Russia. It is a riddle wrapped in a mystery inside an enigma” (Churchill, 1939). “Once to every man and nation comes the moment to decide”.