The Jeep community has developed abbreviations for various Jeep models, some of which are used on this site, here they are:

XJ - Regular Cherokee  '84 - '01
ZJ - Older Grand Cherokee '93 - '98
WJ - New Grand Cherokee '99+
YJ - Older Wrangler '87 - '95
TJ - New Wrangler '97+
MJ - Comanche '86 - '92
DJ - Postal Jeep
CJ-5 - Civilian Jeep ?? - '75
CJ-7 - Civilian Jeep '76 - '86
SJ - Old Wagoneer
KJ - Liberty '02+