Colloquial term for a pachinko parlor. The パチ part is a shortening of パチンコ, and 屋 is a common suffix for shops or establishments.
That pachinko parlor is always crowded, isn't it?
A new pachinko parlor opened in front of the station.
Clipping of パチンコ (pachinko) + 屋 (shop). The exact origin of the clipping is uncertain, but it follows a common pattern in Japanese slang of shortening longer loanwords.