enigma
enigma (e*nig"mȧ) , noun
[Latin aenigma, Greek a'i`nigma, from a'ini`ssesqai to speak darkly, from a'i^nos tale, fable.]
1.
A dark, obscure, or inexplicable saying; a riddle; a statement, the hidden meaning of which is to be discovered or guessed.
A custom was among the ancients of proposing an enigma at festivals.
2.
An action, mode of action, or thing, which cannot be satisfactorily explained; a puzzle; as, his conduct is an enigma.