n. Abbreviation of difference.n. Any program which compares two files or sets of files and outputs a description of the differences between them.n. The output of a diff program. A diff file.n. Abbreviation of differential: differential of types of white blood cell in a complete blood count.n. Abbreviation of difficult.n. A difficult route.v. To run a diff program on (files or items).v. To produce a description of changes made to a collection of files. To produce a patch file.v. To compare two files or other objects, manually or otherwise.proper-noun. A program, historically part of the Unix operating system, which compares two files or sets of files and outputs a description of the differences between them.