It’s an unauthorized copy of a kit or prop. In simple terms, recasting happens when unscrupulous individuals obtain an original of a model and use it as a master to make their own mold and produce cheap knock-offs. These copies are referred to as "recasts."
Recasts are ALWAYS (but not always, I will explain why in next page) inferior to the original model. Just as a photocopy of photocopy is worse than a photocopy of an original, a recast of a kit is necessarily worse than a casting that comes from a mold made using the original prototype. Detail and crispness is always lost. Add to that the fact that re-casters don’t really care about the modeler, but only making a quick buck, and therefore do things like: use cheap materials (e.g., brittle, bad-smelling resin and poor quality metals); do slip shod quickly casting jobs (e.g., resulting in offset seams, pin holes, and uncured spots); use molds that are worn out (silicone molds start to break down after a certain number of castings from the heat generated as the resin sets or metal heat); don’t bother to produce unusual parts (e.g., plastic or vacuform plastic accessories); and don’t bother to produce box art or even include a box with the kit. The re-caster will just steal someone else’s work. Some of the worst quality recasts of this sort are those that one cannot help but run into on E-Bay: those being sold by re-casters in Thailand, Singapore, and other places in Asia. But the situation is changing, and in the past years a lot of recasts are coming mainly from Spain followed by UK, but also from France, Germany, Italy and a few from Serbia or similar countries. China and Russia are now leaders with resin models.

There are 4 type of recasters I can define:

 

• PERSONAL - people who recast for their only use not for profit (still not legal be aware)

• HOBBIST - people using cheap ways to make quick copies, mainly resin since it is easier and cheaper, or use
  gravity pouring for metals.

• ADVANCED - professionals or in most cases private people using professional service to make good quality copies.

• CORPORATES - Actual companies producing industrial quantities of models.