  We present the first detection of cool, neutral gas in the outskirts of low-z
galaxy clusters using a statistically significant sample of 3191 z$\approx$0.2
background quasar - foreground cluster pairs by cross-matching the Hubble
Spectroscopic Legacy Archive quasar catalog with optically- and SZ-selected
cluster catalogs. The median cluster mass of our sample is $\approx 10^{14.2}$
M_sun, with a median impact parameter ($\rho_{cl}$) of $\approx5$ Mpc. We
detect significant Lya, marginal CIV, but no OVI absorption in the
signal-to-noise ratio weighted mean stacked spectra with rest-frame equivalent
widths of 0.096$\pm$0.011 A, 0.032$\pm$0.015 A, and <0.009 A (3$\sigma$) for
our sample. The Lya REW shows a declining trend with increasing $\rho_{cl}$
($\rho_{cl}$ / $R_{500}$) which is well explained by a power-law with a slope
of -0.79 (-0.70). The covering fractions (CFs) measured for Lya (21\%), CIV
(10\%) and OVI (10\%) in cluster outskirts are significantly lower than in the
circumgalatic medium (CGM). We also find that the CGM of galaxies that are
closer to cluster centers or that are in massive clusters is considerably
deficient in neutral gas. The low CF of the Lya along with the non-detection of
Lya signal when the strong absorbers (N(HI) > $10^{13} cm^{-2}$) are excluded,
indicate the patchy distribution of cool gas in the outskirts. We argue that
the cool gas in cluster outskirts in combination arises from the circumgalactic
gas stripped from cluster galaxies and to large-scale filaments feeding the
clusters with cool gas.
