flu /fluː/noun 2forms 1phrases 1 noun2 •an illness that spreads easily from person to person and makes someone feel hot and weak for daysHe missed work because he caught the flu.Every winter, doctors warn about seasonal flu. •(informal) Stomach flu. formsflus Phrases with flu diplomatic fluAn illness feigned by one or more government officials or other public figures as an excuse for an absence really based on political factors.
