The word "systemwide" means something that applies to or affects an entire system or organization, rather than just a small part of it. Full definition
Last year, though, the major benefit of systemwide upgrades (SWUs) was cut in half from 8 to 4. (upgradedpoints.com)
American AAdvantage already reduced the number of systemwide upgrades it would issue to Executive Platinum members and their unlimited domestic upgrades. (travelcodex.com)
Update 11/5/16: AA has reached out to clarify the procedure for systemwide upgrades, explaining «For now, when Premium Economy goes into service, our customers will continue to upgrade from main cabin to business class. (thepointsguy.com)