Synecdoche: The 12th Man
From English Composition and Rhetoric, by Alexander Bain; English Composition by W. Davidson; Practical Rhetoric, by Albert Raub:Synecdoche (Greek synekdoche, ‘to receive together’) is a figure which represents a part for the whole or the whole for a part, as in
The Twelfth Man (part)
for
Seahawks’ fans (whole)