The Free On-line Dictionary of Computing (30 December 2018):

Wi-Fi Protected Access Pre-Shared Key
WPA Pre-Shared Key
WPA-PSK

    (WPA-PSK) A simplified but still
   powerful form of WPA, most suitable for home wireless
   networking.  As with WEP, you set a static key or pass
   phrase, but WPA-PSK uses TKIP to automatically change the
   keys periodically, making it much more difficult to break the
   encryption.

   (2007-05-11)