2. Puzzle, riddle, enigma refer to something baffling or confusing that 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 one's ingenuity: a crossword puzzle; The reason for their behavior remains a puzzle. A riddle is an intentionally obscure statement or question, the meaning of or answer to which is to be arrived at only by guessing: the famous riddle of the Sphinx. Enigma, originally meaning riddle, now refers to some baffling problem with connotations of mysteriousness: He will always be an enigma to me.

Did you mean unsling?