(in ancient Egypt)

a figure of an imaginary creature having the head of a man or an animal and the body of a lion.

( usually initial capital letter ) the colossal recumbent stone figure of this kind near the pyramids of Giza.

( initial capital letter ) Classical Mythology . a monster, usually represented as having the head and breast of a woman, the body of a lion, and the wings of an eagle. Seated on a rock outside of Thebes, she proposed a riddle to travelers, killing them when they answered incorrectly, as all did before Oedipus. When he answered her riddle correctly the Sphinx killed herself.

any similar monster.

a mysterious, inscrutable person or thing, esp. one given to enigmatic questions or answers.