Derez (short for Deresolution) is a term used to describe someone or something disappearing or dissolving, essentially resulting in deletion. It is a program's equivalent of death or the destruction of a building or vehicle. The opposite of "derez" is Rez, a program's equivalent of birth, or loading/starting a program in the system.
The word is derived from deresolve, first referenced in TRON when conscripts received their identity disc:
"If you lose your disc, or fail to follow commands, you will be subject to immediate deresolution." - Sark
When programs derez in TRON, their circuits fade to darkness and they compress into a flash of light which winks upwards before disappearing entirely. Sometimes, they are enveloped in a red or yellow glow before they disappear. If they slowly derez from grievous injuries or from being decompiled, their circuitry may pulse slowly, dimming until it fades out, and their data scatters into the surrounding terrain as they deresolve.
When programs derez in TRON: Legacy, they shatter into thousands of cubical voxels, which scatter on the ground like broken glass. The cube-like voxels appear to remain on the Grid after deresolution. The shattering of fast-moving vehicles, due to the energy involved in their destruction, appears similar to a liquid splash which rises from the impact and then dissipates. Both voxels and energy splashes reflect the circuit color of the derezzing individual or object.
Deresolution in TRON: Uprising is much the same as it is in TRON: Legacy. However, it is also mentioned that programs can be derezzed "bit by excruciating bit", as opposed to an instantaneous and comprehensive shatter. This may refer to the decompiler used to suck both energy and data out of programs, leaving them empty, colorless husks which shatter into dust instead of voxels.
Note: The following section contains information that appears in the TRON 2.0 storyline, which has been classed as non-canon with the TRON mythology and takes place in an alternate timeline.
If the digitization hardware is available, should a user derez in the Game Grid, he or she will be simply returned to the real world. However if the digitization hardware or software is damaged or missing, the user will die.
TRON 2.0 information ends here.
The MCP believed that a user such as Kevin Flynn could be killed on the Game Grid.
A user on Flynn's Grid can be injured, and presumably derezzed. However, a damaged user bleeds, as Sam Flynn did when Rinzler slashed his arm, instead of shedding the glass-like bits created when programs are damaged.