Nano disintegration is a method of execution.
The ugly physical part
The subject is injected or sprayed with a solution containing millions of nanobots (Nanolysins) which have been programmed to break down any organic matter they come into contact with. What follows is a particularly painful and unpleasant death as the victim is effectively melted down on the spot over a period of two to three minutes.
Nano disintegration is sometimes used as an assassination tool, as the only remains of the victim are a puddle of foul-smelling fluid, their clothing and any implants they had. All of which can be quickly and easily disposed of, leaving very little evidence that the assassination has taken place.
Gallente-Caldari war catalyst
The most famous person to be killed in this way was Admiral Alexander Noir, who was murdered in his own home by the Broker as part of a plot to spark a second war between the Gallente Federation and the Caldari State by crashing the FNS Wandering Saint into the Ishukone Headquarters in the Malkalen system.