Metonomy

n. A figure of speech in which one word or phrase is substituted for another with which it is closely associated, as in the use of Washington for the United States government or of the sword for military power.

n. In rhetoric, change of name; a trope or figure of speech that consists in substituting the name of one thing for that of another to which the former bears a known and close relation.

n. A trope in which one word is put for another that suggests it

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