  Obscuring winds driven away from active supermassive black holes are rarely
seen due to their transient nature. They have been observed with
multi-wavelength observations in a few Seyfert 1 galaxies and one broad
absorption line radio-quiet quasar so far. An X-ray obscuration event in MR
2251-178 was caught in late 2020, which triggered multi-wavelength (NIR to
X-ray) observations targeting this radio-quiet quasar. In the X-ray band, the
obscurer leads to a flux drop in the soft X-ray band from late 2020 to early
2021. X-ray obscuration events might have a quasi-period of two decades
considering earlier events in 1980 and 1996. In the UV band, a forest of weak
blueshifted absorption features emerged in the blue wing of Ly$\alpha$
$\lambda1216$ in late 2020. Our XMM-Newton, NuSTAR, and HST/COS observations
are obtained simultaneously, hence, the transient X-ray obscuration event is
expected to account for the UV outflow, although they are not necessarily
caused by the same part of the wind. Both blueshifted and redshifted absorption
features were found for He {\sc i} $\lambda10830$, but no previous NIR spectra
are available for comparison. The X-ray observational features of MR 2251-178
shared similarities with some other type 1 AGNs with obscuring wind. However,
observational features in the UV to NIR bands are distinctly different from
those seen in other AGN with obscuring winds. A general understanding of the
observational variety and the nature of obscuring wind is still lacking.
