A synecdoche is a figure of speech or expression used to denote and in some case define a person or a whole object. Effectively it works as a de facto name, often including a characteristic of the object. The usage is bordering on slang, but can be efficient when it's used as a briefer version of a formal usage like a long name or technical/scientific taxonomic descriptor. Some synecdoches are in fact acronyms turned into 'names'.
Examples of Synecdoche:
|GUI- Graphic user interface, now commonly called GUI, 'gooey'.|
Bucky Balls: Highly symmetrical spherical polymer, properly known as Buckminster Fullerene.
Nicknames are used as synecdoches for people.
Graphic user interface of a typical text processor.