Definition of "sphinx"

[W]hatsoe'er of strange / Sculptured on alabaster obelisk, / Or jasper tomb, or mutilated sphynx, / Dark Æthiopia in her desert hills. / Conceals.

1815 September 10 – December 14, Percy Bysshe Shelley, “Alastor; or, The Spirit of Solitude”, in Alastor; or, The Spirit of Solitude: And Other Poems, London: […] Baldwin, Cradock, and Joy, […]; and Carpenter and Son, […] [b]y S. Hamilton, […], published 1816, page 9

...it is clear that judges are no longer required to be as passive as they once were; to be what I call sphinx judges. We now not only accept that a judge may intervene in the adversarial debate, but also believe that it is sometimes essential for him to do so for justice in fact to be done.

1985 February 21, Antonio Lamer, “Brouillard Also Known As Chatel v. The Queen, 1985 CanLII 56 (SCC)”, in CanLII‎, retrieved 22 October 2021

Constance said boastfully, ‘My sphinxes are strong and in good repair. I order you to come.’

1982, Lawrence Durrell, Constance (Avignon Quintet), Faber & Faber, published 2004, page 836

The sphinxèd riddle of the Universe,Nature's unsolved enigma, who may prove?

1900, Leigh Gordon Giltner, “Love and Death”, in The Path of Dreams: Poems, page 27

Then there are the folks trying to do a Garbo on us […] Janet Gaynor, so they tell, is sphinxing it and has gone into a Retirement, with "Nothing to Say — Please Go Away" written on the doormat.

1933 February, Gladys Hall, “The Hollywood Frivolities of 1932”, in Motion Picture, volume 45, page 29

What with Fisher whole-hogging on one side, and K. of K. sphinxing on the other, Churchill had his work cut out to get any sort of agreement at all.

1964, John Hargrave, The Suvla Bay Landing, page 22

Perhaps Nature is sphinxing us on purpose. Whatever her objects may be, perhaps she gets her work done better when she appeals to our gambling instincts. If you knew for certain exactly how your marriage was going to turn out […]

1933, Roycroft Junto Outlines, The Roycrofters, page 412

And then he summarizes his fears with a reference to that icon which […] stood for the feminine threat to civilization: “Crowds are somewhat like the sphinx of ancient fable: it is necessary to arrive at a solution of the problems offered by their psychology or to resign ourselves to being devoured by them.” Male fears of an engulfing femininity are here projected onto the metropolitan masses, who did indeed represent a threat to the rational bourgeois order. […] We may want to relate Le Bon's social psychology of the masses back to modernism's own fears of being sphinxed.

1986, Andreas Huyssen, After the Great Divide: Modernism, Mass Culture, Postmodernism, page 53