Metonymy is a figure of speech in which one thing is referred to by the name of something closely connected to it, such as an object, place, institution, or attribute. Poets use metonymy to compress meaning and suggest a larger idea through a related detail. It is different from synecdoche, which uses a part to stand for a whole.
Example
The stage went silent when the curtain fell.
The pen in the corner had already made its decision.
"The Crown" for the British monarchy.
"The press" for the news media.
"A dish" for an entrée.
"The Pentagon", a building, to refer to the organization that occupies it, the U.S. Department of Defense.
"The White House" for the President of the United States and his administration, by the same token as above.
Related Definitions
[n] substituting the name of an attribute or feature for the name of the thing itself (as in `they counted heads')