diff

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Difference.

from The Century Dictionary.

• noun An abbreviation of difference, different, or differs.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun slang Abbreviation of difference.
• noun computing Any program which compares two files or sets of files and outputs a description of the differences between them.
• noun computing The output of a diff program. A diff file.
• noun medicine Abbreviation of differential: differential of types of white blood cell in a complete blood count.
• noun slang Abbreviation of difficult.
• noun rock climbing A difficult route.
• verb transitive, computing To run a diff program on (files or items).
• verb transitive, computing To produce a description of changes made to a collection of files. To produce a patch file.
• verb transitive, computing To compare two files or other objects, manually or otherwise.
• proper noun computing 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.