Void Out
A void out is term used when Jak dies in a void plane that he is actively navigating through to warp to the most recent checkpoint.
Void outs are only useful in two scenarios. The first is the elevator skip when entering Lost Precursor City. The second is the Forbidden Jungle temple void out, which is only theoretically useful in the Low Eco category.
Demonstration
Technical
When levels are stacked vertically on top of each other, the bottom level tends to be located within the top level's void area. If Jak is navigating through the lower level while the upper level is still loaded in, Jak is technically walking through the void area of the upper level. The void out sequence only triggers once Jak has been airborne within the void area for 2 seconds. Otherwise, he is free to move around. Ledge grabbing is considered airborne in this scenario.
If Jak passes through a void plane while in a grounded state, he will not immediately die and will be able to move through the void plane. This is why Jak does not die when taking elevators into lower levels.
Load Boundaries
When going down the Forbidden Jungle elevator into the temple below, Jak and the camera will pass through 3 load boundaries: a white ,code>load boundary, a yellow display boundary, and a red vis boundary. These load boundaries are for fully loading in the temple portion. For unknown reasons, there is a chance that the game will not register Jak or the camera passing through some of the boundaries. If the game fails to register Jak and the camera passing through red load boundary, the setup will be complete for a void out to occur.
Discovery
Void outs have happened to people during casual play, especially the one in the Forbidden Jungle temple. Because of this, it is impossible to determine who it happened to first.