It means the instance crashed. When it happens, everyone in the instance is booted to character select, and the instance is lost/reset. It only affects people in that instance, though. And instance crashes also result in partial rollbacks--everything that happened (looted items, consumed items, etc.) within a certain time before the crash won't have been saved and is lost as well.
We had that happen on one vMoL run about a month or so ago. And I remember back when Orsinium came out, there was an issue that was causing a ton of instance crashes in the 4-man dungeons--we had pledges that didn't complete and final boss loot that was lost because the instance would crash at the very end. They hotfixed that within a few days, as I recall. Ever since then, I've only had one or two instance crashes--they're annoying as hell, but relatively rare.
timidobserver wrote: »Tank lost taunt on ZOS.