Spanish flu

noun

Span·​ish flu

ˈspan-ish-

variants also Spanish influenza

: influenza that is caused by a subtype (H1N1) of an orthomyxovirus (Alphainfluenzavirus influenzae) causing influenza A and that was responsible for about 500,000 deaths in the United States in the influenza pandemic of 1918–1919 compare asian flu, hong kong flu