Definition of "metonym"

...to say that "New York was thrown into a state of great excitement," when we mean the inhabitants of New York, is technically to use the metonym of putting "the container for the thing contained."

1891 September, William Minto, “Practical talks on writing English”, in Theodor Flood, editor, The Chautauquan, volume 13, pages 279–280

She not only outlines the devastating effects of seferberlik but also highlights the changing meaning of this term - as it acquired a civilian dimension in its Arabic rendition (safar barlik) - and its potency as a metonym for the war as a whole.

2014 November, Melanie Schulze Tanielian, “Feeding the city: The Beirut Municipality and the politics of food during World War I”, in International Journal of Middle East Studies, volume 46, number 4, pages 737–758

Chapter 1, using the railway as a metonym, explored the relationship between past and present, and argued that diachronic, or historical, time was dissolved in the proliferation of present moments, or synchronic time.

2011, Geraldine Lawless, Modernity's Metonyms: Figuring Time in Nineteenth-century Spanish Stories, Lewisburg, PA: Bucknell University Press, page 155