  We predicted a stellar occultation of the bright star Gaia DR1
4332852996360346368 (UCAC4 385-75921) (m$_{\rm V}$= 14.0 mag) by the centaur
2002 GZ$_{32}$ for 2017 May 20$^{\rm th}$. Our latest shadow path prediction
was favourable to a large region in Europe. Observations were arranged in a
broad region inside the nominal shadow path. Series of images were obtained
with 29 telescopes throughout Europe and from six of them (five in Spain and
one in Greece) we detected the occultation. This is the fourth centaur, besides
Chariklo, Chiron and Bienor, for which a multi-chord stellar occultation is
reported. By means of an elliptical fit to the occultation chords we obtained
the limb of 2002 GZ$_{32}$ during the occultation, resulting in an ellipse with
axes of 305 $\pm$ 17 km $\times$ 146 $\pm$ 8 km. From this limb, thanks to a
rotational light curve obtained shortly after the occultation, we derived the
geometric albedo of 2002 GZ$_{32}$ ($p_{\rm V}$ = 0.043 $\pm$ 0.007) and a 3-D
ellipsoidal shape with axes 366 km $\times$ 306 km $\times$ 120 km. This shape
is not fully consistent with a homogeneous body in hydrostatic equilibrium for
the known rotation period of 2002 GZ$_{32}$. The size (albedo) obtained from
the occultation is respectively smaller (greater) than that derived from the
radiometric technique but compatible within error bars. No rings or debris
around 2002 GZ$_{32}$ were detected from the occultation, but narrow and thin
rings cannot be discarded.
