Oxford Definition: "a word or phrase in which a part of something is used to represent a whole, or a whole is used to represent a part of something."
Oxford Dictionary. Oxford UP, www.oxfordlearnersdictionaries.com/us/definition/english/synecdoche?q=Synecdoche.
Informal Definition: a word that usually means the entire thing but it’s used to represent only a smaller part.
Example: "Australia lost by two goals, Australia is used to represent the Australian team."
Oxford Dictionary UP. www.oxfordlearnersdictionaries.com/us/definition/english/
synecdoche?q=Synecdoche.
Etymology:
From the Greek word synekdokhe (συνεκδοχή in Greek), meaning 'putting a whole for a part'
“Its usage in English dates back to the 15th century when it came to describing a figure of speech in which the part is taken for the whole or vice versa.”