flu /fluː/ BrE AmE noun [uncountable]
[ Date: 1800-1900 ; Origin: influenza ]
a common illness that makes you feel very tired and weak, gives you a sore throat, and makes you cough and have to clear your nose a lot SYN influenza :
Steven’s still in bed with flu.
She’s got the flu.
I couldn’t go because I had flu.
a flu virus/bug
the spread of the flu virus
Doctors now fear a flu epidemic.