1. Informal A change to a program—usually to correct some error—that is introduced in a manner that emphasizes usability and performance rather than security, and is intended to effect only a temporary repair. Even where a program is written in some high-level language, the patching might be carried out in machine-code terms on the compiled version of the program. Often during testing a series of minor errors will be corrected by patching in order to permit testing to continue without the delay of recompilation. Subsequently the corresponding changes will all be incorporated into the program source text. Patches may be installed manually or using patch management software. Though meant to fix errors, poorly designed patches are often the cause of security breaches and other problems.

2. (surface patch) A boundary piece of a surface. Patches are descriptions of three-dimensional shapes specified as bounded equations with criteria for joining other patches along their edges; for example, for smooth surfaces the patch equations must be differentiable at the edge. Complex surfaces are often broken down into patches. The whole surface is then described by the collection of patches. There is a wide variety of techniques for defining patches, for example Coons patches and Bézier patches. Patches are widely used in computer-aided design to describe curved surfaces and complex smooth geometries.