AcronymGenie is a small and free program that will let you look up the expansion of a computer acronym. An acronym is a word made up of the initial letters of a series of words. For example, ISP is an acronym for Internet Service Provider.
AcronymGenie covers most of the computer-related fields, including Internet, chat, programming, networking, graphics etc.
To find out what, e.g., USB stands for, simply type the letters U-S-B in AcronymGenie, and it will show you the expansion Universal Serial Bus.